Synthesis of a doubly thermo-responsive schizophrenic diblock copolymer based on poly[N-(4-vinylbenzyl)-N,N-diethylamine] and its temperature-sensitive flip-flop micellization

Synthesis of a doubly thermo-responsive schizophrenic diblock copolymer, poly( tert -butyl methacrylate)- block -poly[ N -(4-vinylbenzyl)- N , N -diethylamine] (P t BMA- b -PVEA), by reversible addition–fragmentation chain transfer (RAFT) polymerization and its temperature-sensitive flip-flop micellization are discussed. By employing 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid as the RAFT agent, the schizophrenic P t BMA- b -PVEA diblock copolymers with different block lengths were prepared. The poly( tert -butyl methacrylate) (P t BMA) block exhibits insoluble-to-soluble phase transition at the upper critical solution temperature (UCST) and the poly[ N -(4-vinylbenzyl)- N , N -diethylamine] (PVEA) block exhibits soluble-to-insoluble phase transition at the lower critical solution temperature (LCST) in methanol, respectively. At temperatures below the UCST of the P t BMA block, P t BMA@PVEA micelles containing a P t BMA core and a PVEA corona are formed in methanol. At temperatures above the UCST of the P t BMA block while below the LCST of the PVEA block, P t BMA- b -PVEA is molecularly soluble in methanol. At temperatures above the LCST of the PVEA block, inverse PVEA@P t BMA micelles containing a PVEA core and a P t BMA corona are formed. The polymerization degree of the P t BMA block or the PVEA block affecting the UCST/LCST of the schizophrenic diblock copolymer and the size of the P t BMA@PVEA or PVEA@P t BMA micelles is investigated.