Synthesis of Thermo-Responsive Polymers With Both Tunable UCST and LCST

New water-soluble block copolymers of 2-(2-methoxyethoxy)ethyl methacrylate (MEO(2)MA), oligo(ethylene glycol) methacrylate (OEGMA), and N-(3-(dimethylamino) propyl) methacrylamide (DMAPMA) (poly(OEGMA-co-MEO(2)MA)-b-poly(DMAPMA)) were prepared via sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. Selective quaternization of poly(DMAPMA) block gives poly(OEGMA-co-MEO2MA)-b-poly((3-[N-(3-methacrylamidopropyl)- N,N-dimethyl]ammoniopropane sulfonate)-co-N-(3-(dimethylamino) propyl) methacrylamide), such block copolymer exhibits double thermo-responsive behavior in water, poly(MEO(2)MA-co-OEGMA) block shows a lower critical solution temperature (LCST), and poly((3-[N-(3-methacrylamidopropyl)- N, N-dimethyl] ammoniopropane sulfonate)- co-N-(3-(dimethylamino) propyl) methacrylamide) block shows a upper critical solution temperature (UCST). Both of LCST and UCST can be controlled: LCST could be tuned by the fraction of OEGMA units in poly(OEGMA-co-MEO(2)MA), and UCST was found to be dependent on the degree of quaternization (DQ).