Diblock copolymers consisting of a polymerized ionic liquid and poly(N-isopropylacrylamide). Effects of PNIPAM block length and counter ion on self-assembling and thermal properties.

Amphiphilic diblock copolymers composed of a polymeric ionic liq., PIL, and poly(N-isopropylacrylamide), PNIPAM, have been synthesized using RAFT reactions. The length of the PIL block was kept const. while the mol. mass of the PNIPAM block was varied. The PIL was poly(2-(1-butylimidazolium-3-yl)ethyl methacrylate tetrafluoroborate) which is insol. in water owing to the bulky hydrophobic counterion. When the PNIPAM block was long enough, the polymers formed spherical micelles in water, which showed thermally responsive behavior. Colloidally stable particles could be prepd. also from the homopolymer PIL. PNIPAM affects noticeably the properties of the PIL, and also the polycation has a strong effect on the thermal properties of PNIPAM in aq. dispersions. As a ref., a polymer where bromide was the counterion instead of the tetrafluoroborate ion was synthesized, providing a water sol. PIL block. The core-shell micelles formed by amphiphilic block copolymers in pure water and those by double-hydrophilic polymers in aq. NaBF4 undergo partial structural inversion upon the thermal collapse of PNIPAM. [on SciFinder(R)]