A New Family of Thermo-Responsive Polymers Based on Poly[N-(4-vinylbenzyl)-N,N-dialkylamine]

A new family of the thermo-responsive polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] with the pendent amine group as well as the doubly thermo-responsive triblock copolymer were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. These polymers showed the lower critical solution temperature (LCST) and/or the upper critical solution temperature (UCST) in alcohol and in the alcohol/water mixture. The polymer molecular weight, the polymer concentration, the cosolvent/nonsolvent and the deuterated solvent affecting the LCST and/or UCST were investigated, and their great influence on the LCST/UCST was demonstrated. The origin of the phase transition of poly[N-(4-vinylbenzyl)-N,N-dialkylamine] at LCST upon heating was investigated and the possible reason was proposed. The doubly thermo-responsive triblock copolymer of PVMA(53)-b-PVEA(108)-b-PVMA(53) underwent phase transition at two LCST temperatures. The PVEA(108) block underwent the initial phase transition at the first LCST of 32.5 degrees C to form core-corona micelles, and then the subsequent phase transition of the PVMA(53) block took place at the second LCST of 54.5 degrees C to produce corona collapsed micelles. The proposed polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] are anticipated to broaden the thermo-responsive polymer range and will be useful in polymer science.