Low temperature ATRP of POSS‐MA and its amphiphilic pentablock copolymers

Abstract

A low temperature ATRP of methacryloisobutyl POSS (POSS‐MA) is carried out, using poly(propylene glycol) (PPG)‐based macroinitiator, in toluene with CuCl/PMDETA as the catalyst system, generating well‐defined P(POSS‐MA)‐b‐PPG‐b‐P(POSS‐MA) triblock copolymer with Ð ~ 1.1. The semilogarithmic kinetic plot reveals first‐order kinetics and the dispersity is observed to decrease as the reaction progresses—an indication of the controlled behavior of the polymerization. To assess the chain‐end fidelity of the produced block copolymer, chain extension is carried out with oligo(ethylene glycol methacrylate) (OEGMA) that afforded water‐soluble P(OEGMA)‐b‐P(POSSMA)‐b‐PPG‐b‐P(POSSMA)‐b‐P(OEGMA) pentablock copolymers. The SEC profiles suggest a quantitative initiation by the macroinitiator. By varying the monomer to initiator molar ratio, block copolymers with various P(OEGMA) chain lengths, ranging from 19 to 58 units on each side have been achieved with relative lower dispersity (Ð < 1.4). Kinetic analysis of the ATRP of OEGMA, with P(POSSMA)‐b‐PPG‐b‐P(POSSMA) as the macroinitiator, suggests first‐order kinetics and controlled nature of the polymerization. The PPG and P(OEGMA) segments impart a thermosensitive character to the obtained water‐soluble amphiphilic hybrid block copolymers; hence they display temperature‐dependent self‐assembly behavior in aqueous medium.