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

Polysulfobetaines, polymers carrying highly\ud polar zwitterionic side chains, present a promising research\ud field by virtue of their antifouling properties, hemocompatibility,\ud and stimulus-responsive behavior. However, limited\ud synthetic approaches exist to produce sulfobetaine copolymers\ud comprising hydrophobic components. Postpolymerization\ud modification of an activated ester precursor, poly-\ud (pentafluorophenyl acrylate), employing a zwitterionic\ud amine, 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate,\ud ADPS, is presented as a novel, one-step synthetic\ud concept toward sulfobetaine (co)polymers. Modifications were\ud performed in homogeneous solution using propylene carbonate\ud as solvent with mixtures of ADPS and pentylamine,\ud benzylamine, and dodecylamine producing a series of well-defined statistical acrylamido sulfobetaine copolymers containing\ud hydrophobic pentyl, benzyl, or dodecylacrylamide comonomers with well-controllable molar composition as evidenced by NMR\ud and FT-IR spectroscopy and size exclusion chromatography. This synthetic strategy was exploited to investigate, for the first\ud time, the influence of hydrophobic modification on the upper critical solution temperature (UCST) of sulfobetaine copolymers\ud in aqueous solution. Surprisingly, incorporation of pentyl groups was found to increase solubility over a wide composition range,\ud whereas benzyl groups decreased solubilityan effect attributed to different entropic and enthalpic contributions of both\ud functional groups. While UCST transitions of polysulfobetaines are typically limited to higher molar mass samples, incorporation\ud of 0−65 mol % of benzyl groups into copolymers with molar masses of 25.5−34.5 kg/mol enabled sharp, reversible transitions\ud from 6 to 82 °C in solutions containing up to 76 mM NaCl, as observed by optical transmittance and dynamic light scattering.\ud Both synthesis and systematic UCST increase of sulfobetaine copolymers presented here are expected to expand the scope and\ud applicability of these smart material

The synthesis and aqueous solution properties of a family of zwitterionic homo-, co-, and terpolymers derived from poly(2-vinyl-4,4-dimethylazlactone) (pVDMA) with tunable lower and upper critical solution temperatures (LCST and UCST) are presented. A RAFT-made pVDMA precursor was reacted with mixtures of zwitterionic sulfopropylbetaine (SPB) amine or sulfobutylbetaine (SBB) amine, tetrahydrofurfurylamine (THF amine), and benzylamine (Bz amine) in varying molar ratios. Products were characterized by variable temperature (VT) NMR spectroscopy, FT-IR spectroscopy, size exclusion chromatography, turbidity, and VT dynamic light scattering in order to confirm quantitative postpolymerization modification, determine molar compositions, and elucidate structure−property relationships. Polymers comprising large molar fractions of THF groups showed LCST behavior due to a polarity change of the THF-functional segments, while SPB/SBB-rich samples, including the zwitterionic homopolymers, showed UCST behavior in ultrapure water based on electrostatic polymer−polymer attractions. Binary SPB−THF copolymers were water-soluble between 0 and 90 °C for a large compositional range. Terpolymers comprising molar SPB:THF:Bz ratios of approximately 50:25:25 showed a low LCST and a high UCST (LCST < UCST) with a miscibility gap in which the SPB groups and THF groups were not fully hydrated. In the one-phase regions below the LCST and above the UCST, polymer chains were presumed to be unimerically dissolved with partially solvated domains undergoing intrachain associations. Addition of NaCl caused LCST and UCST behavior to disappear, resulting in temperature-independent solubility. Molecular insights presented herein are anticipated to aid in the development of smart materials with double LCST < UCST or UCST < LCST thermoresponsiveness.