Reversible Hydrogels from an Ampholytic A_<i>n</i>(B<i>‐b‐</i>C)_<i>n</i> Heteroarm Star Block Terpolymer

Abstract

Abstract An asymmetric, amphiphilic, A n (B‐ b ‐C) n heteroarm star block terpolymer bearing polystyrene and poly(2‐vinyl pyridine)‐ block ‐poly(acrylic acid) arms, was synthesized by anionic polymerization, using an extending “in‐out” method and a post polymerization deprotection reaction. Due to the pH‐dependent protonation/deprotonation equilibrium of the P2VP/PAA blocks, a rich phase behavior was observed as a function of pH. At pH = 2, the star terpolymers form a physical hydrogel through a solvent‐induced sol/gel transition in a DMF/water solvent mixture. The gelation mechanism was attributed to a jamming effect mediated by increasing the dielectric permittivity of the medium. magnified image