Hydrophobically Modified Sulfobetaine Copolymers with Tunable Aqueous UCST through Postpolymerization Modification of Poly(pentafluorophenyl acrylate)

摘要

Polysulfobetaines, polymers carrying highlyudpolar zwitterionic side chains, present a promising researchudfield by virtue of their antifouling properties, hemocompatibility,udand stimulus-responsive behavior. However, limitedudsynthetic approaches exist to produce sulfobetaine copolymersudcomprising hydrophobic components. Postpolymerizationudmodification of an activated ester precursor, poly-ud(pentafluorophenyl acrylate), employing a zwitterionicudamine, 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate,udADPS, is presented as a novel, one-step syntheticudconcept toward sulfobetaine (co)polymers. Modifications wereudperformed in homogeneous solution using propylene carbonateudas solvent with mixtures of ADPS and pentylamine,udbenzylamine, and dodecylamine producing a series of well-defined statistical acrylamido sulfobetaine copolymers containingudhydrophobic pentyl, benzyl, or dodecylacrylamide comonomers with well-controllable molar composition as evidenced by NMRudand FT-IR spectroscopy and size exclusion chromatography. This synthetic strategy was exploited to investigate, for the firstudtime, the influence of hydrophobic modification on the upper critical solution temperature (UCST) of sulfobetaine copolymersudin aqueous solution. Surprisingly, incorporation of pentyl groups was found to increase solubility over a wide composition range,udwhereas benzyl groups decreased solubilityan effect attributed to different entropic and enthalpic contributions of bothudfunctional groups. While UCST transitions of polysulfobetaines are typically limited to higher molar mass samples, incorporationudof 0−65 mol % of benzyl groups into copolymers with molar masses of 25.5−34.5 kg/mol enabled sharp, reversible transitionsudfrom 6 to 82 °C in solutions containing up to 76 mM NaCl, as observed by optical transmittance and dynamic light scattering.udBoth synthesis and systematic UCST increase of sulfobetaine copolymers presented here are expected to expand the scope andudapplicability of these smart materials