University of Mainz

Postdoc

Peter worked at University of Mainz as a Postdoc

University of New South Wales

Research Associate

Self-Assembly of Functional Polymers,
Thermoresponsive Materials

University of New South Wales

Lecturer/Research Fellow

Novel Smart Materials
Multifunctional Monomers

University of Surrey

Lecturer

Functional Polymers and Nanoparticles
Degradable Polymers
Polymer Photochemistry

Curtin University

Lecturer

Multicomponent Chemistry
Stimulus Responsive Polymers
Postpolymerization Modification

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Eur. Polym. J. 2015, 69, 499–509

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22 °C) for addition of small amounts (e.g. 0.4 mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5 g/L) in response to the addition of as little as 0.4 mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Eur. Polym. J. 2015, 69, 499–509

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22 °C) for addition of small amounts (e.g. 0.4 mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5 g/L) in response to the addition of as little as 0.4 mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

Royal Society of Chemistry/Polymer Chemistry

The multicomponent Passerini reaction of aldehydes, carboxylic acids, and isocyanides is used to produce a series of novel reactive (meth)acrylic and styrenic monomers carrying pendant double bond, (trimethylsilyl protected) triple bond, diene, acetate, or pentafluorophenyl functionality. Dichloromethane and water were compared as solvents in the synthesis of 15 different monomers, with water resulting in significantly higher, up to quantitative, isolated yields with minimal purification. Characterization by 1H, 13C, and 19F NMR spectroscopy, FT-IR spectroscopy and mass spectrometry confirmed the synthesis and high purity of the functional α-acyloxycarboxamide products. The monomers are shown to be well suited for the RAFT-synthesis of well-defined homopolymers, statistical copolymers with methyl methacrylate, poly(ethylene glycol) methyl ether methacrylate, and styrene, statistical copolymers produced from two different Passerini-derived monomers, and AB diblock copolymers. SEC-measured polydispersities were generally low, ĐM ≤ 1.29, and 1H NMR spectroscopy confirmed copolymer molar compositions in good agreement with comonomer feed ratios. We expect this synthetic strategy to provide access to a wide range of novel multifunctional materials and demonstrate preliminary postpolymerization modification of a polystyrene derivative by cleavage of its pendent acetate groups and coupling of the dye Methyl Red to the resulting alcohol groups.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Eur. Polym. J. 2015, 69, 499–509

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22 °C) for addition of small amounts (e.g. 0.4 mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5 g/L) in response to the addition of as little as 0.4 mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

Royal Society of Chemistry/Polymer Chemistry

The multicomponent Passerini reaction of aldehydes, carboxylic acids, and isocyanides is used to produce a series of novel reactive (meth)acrylic and styrenic monomers carrying pendant double bond, (trimethylsilyl protected) triple bond, diene, acetate, or pentafluorophenyl functionality. Dichloromethane and water were compared as solvents in the synthesis of 15 different monomers, with water resulting in significantly higher, up to quantitative, isolated yields with minimal purification. Characterization by 1H, 13C, and 19F NMR spectroscopy, FT-IR spectroscopy and mass spectrometry confirmed the synthesis and high purity of the functional α-acyloxycarboxamide products. The monomers are shown to be well suited for the RAFT-synthesis of well-defined homopolymers, statistical copolymers with methyl methacrylate, poly(ethylene glycol) methyl ether methacrylate, and styrene, statistical copolymers produced from two different Passerini-derived monomers, and AB diblock copolymers. SEC-measured polydispersities were generally low, ĐM ≤ 1.29, and 1H NMR spectroscopy confirmed copolymer molar compositions in good agreement with comonomer feed ratios. We expect this synthetic strategy to provide access to a wide range of novel multifunctional materials and demonstrate preliminary postpolymerization modification of a polystyrene derivative by cleavage of its pendent acetate groups and coupling of the dye Methyl Red to the resulting alcohol groups.

Polymer Analogous Reactions

In: S. Hashimi (ed.). Reference Module in Materials Science and Materials Engineering. 2016, Chapter 01420, Amsterdam: Elsevier BV

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Eur. Polym. J. 2015, 69, 499–509

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22 °C) for addition of small amounts (e.g. 0.4 mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5 g/L) in response to the addition of as little as 0.4 mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

Royal Society of Chemistry/Polymer Chemistry

The multicomponent Passerini reaction of aldehydes, carboxylic acids, and isocyanides is used to produce a series of novel reactive (meth)acrylic and styrenic monomers carrying pendant double bond, (trimethylsilyl protected) triple bond, diene, acetate, or pentafluorophenyl functionality. Dichloromethane and water were compared as solvents in the synthesis of 15 different monomers, with water resulting in significantly higher, up to quantitative, isolated yields with minimal purification. Characterization by 1H, 13C, and 19F NMR spectroscopy, FT-IR spectroscopy and mass spectrometry confirmed the synthesis and high purity of the functional α-acyloxycarboxamide products. The monomers are shown to be well suited for the RAFT-synthesis of well-defined homopolymers, statistical copolymers with methyl methacrylate, poly(ethylene glycol) methyl ether methacrylate, and styrene, statistical copolymers produced from two different Passerini-derived monomers, and AB diblock copolymers. SEC-measured polydispersities were generally low, ĐM ≤ 1.29, and 1H NMR spectroscopy confirmed copolymer molar compositions in good agreement with comonomer feed ratios. We expect this synthetic strategy to provide access to a wide range of novel multifunctional materials and demonstrate preliminary postpolymerization modification of a polystyrene derivative by cleavage of its pendent acetate groups and coupling of the dye Methyl Red to the resulting alcohol groups.

Polymer Analogous Reactions

In: S. Hashimi (ed.). Reference Module in Materials Science and Materials Engineering. 2016, Chapter 01420, Amsterdam: Elsevier BV

Thiol-reactive Passerini-methacrylates and polymorphic surface functional soft matter nanoparticles via ethanolic RAFT dispersion polymerization and post-synthesis modification

Polym. Chem. 2015, 6, 1928–1931

RAFT dispersion polymerization (RAFTDP) is used to prepare reactive nanoparticles via the incorporation of Passerini-derived methacrylic comonomers containing pentafluorophenyl (PFP) groups. Copolymerization of 2-(dimethylamino)ethyl methacrylate with a Passerini comonomer gives copolymers suitable as macro-CTAs for ethanolic RAFTDP of 3-phenylpropyl methacrylate. Reaction of the PFP residues with functional thiols offers an approach for preparing surface modified nanoparticles.

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non-Polar RAFT Dispersion Polymerization and Polymerization-Induced Self-Assembly

J. Polym. Sci. Pol. Chem. 2015, 20, 2326–2335

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non-polar reversible addition-fragmentation chain transfer dispersion polymerization and polymerization-induced self-assembly. Poly(stearyl methacrylate-stat-PFPMA) macro-CTAs, containing up to 12 mol % PFPMA, were used in n-octane and n-tetradecane for the subsequent copolymerization of 3-phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N-dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano-objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of 1H/19F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2326–2335

Novel pH-, Thermo- and Electrolyte-responsive Polymer Gels Derived from a Well-defined, RAFT-synthesized, Poly(2-vinyl-4,4-dimethylazlactone) Homopolymer via One-pot Post-polymerization Modification

Eur. Polym. J. 2015, 62, 204–213

Well-defined stimulus-responsive polymer gels were prepared from poly(2-vinyl-4,4-dimethylazlatone) (PVDMA) via one-pot post-polymerization modification. VDMA homopolymers were reacted with diamine crosslinking agents and functional 1° or 2° amines to form polymer gels that swelled in organic solvents and, in many cases, aqueous solutions. A series of functional amine reagents, including N,N-dimethylethylenediamine (DMEDA), N,N-diethylethylenediamine (DEEDA), morpholine, 3-morpholinopropylamine (MPPA) and tetrahydrofurfurylamine (THFA), were chosen as functional amines to produce polymer gels containing environmentally sensitive species. 13C solid-state NMR and FTIR spectroscopic measurements confirmed complete conversion of the reactive scaffolds. pH-dependent swelling behavior at ambient temperature was observed in DMEDA-, DEEDA- and MPPA-modified hydrogels. Kinetic studies showed the swelling behaviors of DMEDA-modified hydrogels were regulated by cross-linker type and concentration in acidic water (pH = 4) at ambient temperature. The swelling ratio of hydrogels modified by DEEDA, MPPA and THFA also depended strongly on temperature, indicating successful synthesis of thermoresponsive gels. Furthermore, the concentration of added sodium sulfate played a significant role with respect to the swelling properties of MPPA-modified hydrogels. These smart materials may be of interest in the biomedical field as well as in other applications.

ROMP Synthesis of Novel Thermo-, pH- and Salt-responsive (Co)Polymers Containing the Morpholino Functional Group

J. Polym. Sci. Pol. Chem. 2015, 53, 50–58

We report the ring-opening metathesis polymerization (ROMP) synthesis of novel (co)polymers containing the multiresponsive morpholino functional group [(3aR,7aS)−2-(2-morpholinoethyl)−3a,4,7,7a-tetrahydro-1H−4,7-epoxyisoindole-1,3(2H)-dione (M1)]. All (co)polymers were prepared with the Grubbs' first generation initiator, RuCl2(PCy3)2CHPh, in CH2Cl2 or CH2Cl2/2,2,2-trifluoroethanol solvent mixtures. M1 homopolymers exhibit a pH dependent aqueous solubility being fully soluble below pH 5.0 and above pH 6.0. At these intermediate values, the polymers exhibit molecular weight (MW) independent inverse temperature dependent solubility with measured cloud points (TCP) of 86 °C at pH 5.0 and 79 °C at pH 6.0. In the case of the lowest MW homopolymer (absolute MW of 9950 g/mol), there was a clear dependence of the TCP on the homopolymer solution concentration and varied over the range 78–88 °C. The TCP could be further tuned via the preparation of novel AB statistical copolymers. Incorporation of a permanently cationic comonomer as a more hydrophilic species resulted in an increase of the TCP at low incorporations (up to 10 mol %) and the complete disappearance of any temperature dependent solubility at 20 mol %. In a complementary approach, the TCP could also be lowered by the preparation of statistical copolymers of M1 with a more hydrophobic comonomer. Finally, we note that M1 homopolymers are also responsive to Na2SO4 and could be readily salted-out of an aqueous solution salt at a [Na2SO4] of 2.0 M giving a third trigger for controlling aqueous solubility. These copolymers represent examples of new multiresponsive materials and demonstrate the effectiveness of ROMP as a synthetic tool for the preparation of new and interesting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 50–58

The synthesis and aqueous solution properties of sulfobutylbetaine (co)polymers: comparison of synthetic routes and tuneable upper critical solution temperatures

Polym. Chem. 2015, 6, 5705–5718

Polysulfobutylbetaine (SBB) (co)polymers, zwitterionic species bearing ammonium and sulfonate groups separated by a butyl spacer in every repeat unit, were prepared through three different synthetic routes and their aqueous solution behaviour was studied. Postpolymerization quaternization of poly[2-(dimethylamino)ethyl methacrylate] with 1,4-butanesultone resulted in incomplete modification due to the low reactivity of this alkylating agent. RAFT radical polymerization of SBB-functional (meth)acrylate monomers and their copolymerization with a sulfopropylbetaine (SPB) methacrylate yielded well-defined (co)polymers with low dispersities 1.13 ≤ ĐM ≤ 1.23 at monomer conversions of 75–92%. For a series of SBB methacrylate homopolymers with increasing degrees of polymerization from 66–186 measured upper critical solution temperature (UCST) cloud points increased from 27–77 °C. Cloud points of statistical SPB-SBB copolymers with similar degrees of polymerization, but varying molar compositions, increased linearly with SBB content offering a simple means of UCST tuning. Additionally, novel SBB acrylamide homo- and copolymers were prepared by postpolymerization modification of poly(pentafluorophenyl acrylate) with an SBB-functional amine and in mixtures with benzylamine as a hydrophobic modifier. In all cases, the SBB (co)polymers had significantly higher UCSTs than their more common SPB counterparts, greatly extending the temperature range of tuneable UCST transitions and making the investigated SBB (co)polymers advantageous for exploiting their ‘smart’ behaviour. In this respect, combining SBB functionality with hydrophobic benzylacrylamide comonomers is presented as a simple means of increasing the maximum salt concentration at which UCST behaviour (which shows an antipolyelectrolyte effect) can be observed, enabling UCST transitions in aqueous solutions containing a physiological concentration (9 g L−1) of NaCl.

RAFT-prepared α-Difunctional Poly(2-vinyl-4,4-dimethylazlactone)s and their Derivatives: Synthesis and Effect of End Groups on Aqueous Inverse Temperature Solubility

Polym. Chem. 2015, 6, 118–127

A series of five novel R-group di-functional phenyl dithiobenzoates have been prepared and utilized in the controlled reversible addition–fragmentation chain transfer (RAFT) radical polymerization of 2-vinyl-4,4-dimethylazlactone (VDMA), yielding a series of homopolymers of similar average degrees of polymerization but variable α-end group functionality. Each of the reactive polyVDMA homopolymers was reacted with four different small molecule amines: dimethylamine, diethylamine, N,N-diethylethylenediamine and tetrahydrofurfurylamine yielding a series of novel end-functional materials. The effect of the end-groups on the inverse temperature dependent aqueous solubility of the formally hydrophilic homopolymers was then measured and compared to similar materials prepared with benzylpropyltrithiocarbonate as the RAFT agent. In virtually all instances, the introduction of the twin α-end-groups resulted in overall more hydrophobic species that exhibited cloud points spanning the range 25.1–42.7 °C. Importantly, there was a strong influence on the nature of the end groups and the associated solubility characteristics with, in some cases, cloud point behaviour only being observed in polymers with twin end groups while those derived from benzylpropyltrithiocarbonate were fully soluble.

Temperature–heavy metal- and temperature–anion/molecule-responsive systems based on PEG acrylate copolymers containing dipyridyl ligands

Eur. Polym. J. 2015, 69, 499–509

Thermoresponsive copolymers carrying di(2-pyridyl)methyl ligands are shown to respond sensitively and selectively to the presence of heavy metal cations, while their metal complexes respond in a likewise selective and sensitive manner to the presence of anions or molecules with higher metal affinity. A set of well-defined copolymers of poly(ethylene glycol) methyl/phenyl ether acrylate, and N-di(2-pyridyl)methylacrylamide was prepared through a combination of RAFT radical polymerization and postpolymerization modification of activated esters. Products were characterised by 1H and 19F NMR spectroscopy, size exclusion chromatography, FT-IR spectroscopy, and turbidity measurements. Ligand–metal complexation, as observed by UV–vis spectroscopy, was found to increase lower critical solution temperature (LCST) transitions in water drastically (e.g. up to 22 °C) for addition of small amounts (e.g. 0.4 mM) of Cu(II), Co(II), Fe(II) and Ag(I) salts, attributed to a tethering of charge to the polymer. Conversely, salts of Mn(II) and Gd(III) did not affect copolymer solubility. Observed LCST transitions of polymer–metal complexes decreased with the addition of anions or molecules which formed more stable complexes, poorly soluble compounds, or underwent redox reactions with the metal cation. Selectivity toward specific anion or molecule analytes could be tuned though the choice of metal. An isothermal phase separation of a polymer–Cu(II) solution (5 g/L) in response to the addition of as little as 0.4 mM sodium cyanide is demonstrated while the addition of an equal amount of sodium azide did not cause any response, signifying the potential of the proposed concept for sensing applications.

Multicomponent isocyanide-based synthesis of reactive styrenic and (meth)acrylic monomers and their RAFT (co)polymerization

Royal Society of Chemistry/Polymer Chemistry

The multicomponent Passerini reaction of aldehydes, carboxylic acids, and isocyanides is used to produce a series of novel reactive (meth)acrylic and styrenic monomers carrying pendant double bond, (trimethylsilyl protected) triple bond, diene, acetate, or pentafluorophenyl functionality. Dichloromethane and water were compared as solvents in the synthesis of 15 different monomers, with water resulting in significantly higher, up to quantitative, isolated yields with minimal purification. Characterization by 1H, 13C, and 19F NMR spectroscopy, FT-IR spectroscopy and mass spectrometry confirmed the synthesis and high purity of the functional α-acyloxycarboxamide products. The monomers are shown to be well suited for the RAFT-synthesis of well-defined homopolymers, statistical copolymers with methyl methacrylate, poly(ethylene glycol) methyl ether methacrylate, and styrene, statistical copolymers produced from two different Passerini-derived monomers, and AB diblock copolymers. SEC-measured polydispersities were generally low, ĐM ≤ 1.29, and 1H NMR spectroscopy confirmed copolymer molar compositions in good agreement with comonomer feed ratios. We expect this synthetic strategy to provide access to a wide range of novel multifunctional materials and demonstrate preliminary postpolymerization modification of a polystyrene derivative by cleavage of its pendent acetate groups and coupling of the dye Methyl Red to the resulting alcohol groups.

Polymer Analogous Reactions

In: S. Hashimi (ed.). Reference Module in Materials Science and Materials Engineering. 2016, Chapter 01420, Amsterdam: Elsevier BV

Thiol-reactive Passerini-methacrylates and polymorphic surface functional soft matter nanoparticles via ethanolic RAFT dispersion polymerization and post-synthesis modification

Polym. Chem. 2015, 6, 1928–1931

RAFT dispersion polymerization (RAFTDP) is used to prepare reactive nanoparticles via the incorporation of Passerini-derived methacrylic comonomers containing pentafluorophenyl (PFP) groups. Copolymerization of 2-(dimethylamino)ethyl methacrylate with a Passerini comonomer gives copolymers suitable as macro-CTAs for ethanolic RAFTDP of 3-phenylpropyl methacrylate. Reaction of the PFP residues with functional thiols offers an approach for preparing surface modified nanoparticles.

Thiol-reactive Functional Poly(meth)acrylates: Multicomponent Monomer Synthesis, RAFT (Co)polymerization and Highly Efficient Thiol-para-Fluoro Postpolymerization Modification

Polym. Chem. 2015, 6, 436–447

A novel class of thiol-reactive (meth)acrylate monomers and the quantitative postpolymerization modification of their RAFT-made (co)polymers with aromatic, glycosidic, and aliphatic thiols are presented. A set of 6 different N-functional 2-(meth)acryloyloxy-2-(pentafluorophenyl)acetamide monomers bearing pentafluorophenyl groups was prepared by a Passerini three-component reaction of (meth)acrylic acid, 2,3,4,5,6-pentafluorobenzaldehyde, and various isocyanides in water in up to near-quantitative isolated yields. RAFT polymerization was used to produce well-defined homopolymers and copolymers with methyl methacrylate, tert-butyl methacrylate, poly(ethylene glycol methyl ether) (meth)acrylate, and pentafluorophenyl acrylate, with low polydispersity indices of generally ÐM ≤ 1.23. In the presence of base, (co)polymers underwent selective para-fluoro substitution reactions with thiols in the absence of any side reactions observable by 1H and 19F NMR spectroscopy and size exclusion chromatography. The selection of employed thiols included various alkanethiols, a thiolated glucose derivative, mercaptopropionic acid, L-cysteine and the drug captopril. 19F NMR kinetic measurements indicated quantitative thiol–para-fluoro substitutions after <3–80 min at 25–45 °C using 1–1.1 equiv of thiol, depending on the reactivity of the employed thiol (aromatic, glycosidic > primary aliphatic > secondary aliphatic > tertiary aliphatic) and the choice of a suitable base (triethylamine or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)). The versatility of thiol-reactive (meth)acrylate species is demonstrated by the examples of a thermoresponsive copolymer showing a thiol-sensitive lower critical solution temperature (LCST) and the selective sequential modification with thiols and amines of a doubly reactive copolymer containing activated pentafluorophenyl esters.