Effect of architecture on the thermo-induced phase transition of methacrylate-based symmetric pentablock terpolymers

Abstract

A series of six symmetric pentablock terpolymers were synthesised using group transfer polymerisation (GTP). The chemical composition of these terpolymers comprises 45 wt% of oligo(ethylene glycol) methyl ether methacrylate (molar mass = 300 g mol⁻¹, OEGMA300, block A), 30 wt% of n-butyl methacrylate (BuMA, block B), and 25 wt% of di(ethylene glycol) methyl ether methacrylate (DEGMA, block C), aiming at a total molar mass (MM) of 9200 g mol⁻¹ with varied architectures, including ABCBA, CBABC, BCACB, ACBCA, BACAB, and CABAC. The impact of the polymer architecture (specifically the block number and sequence) was evaluated by comparing the properties of these pentablock terpolymers in aqueous solution, including micellisation, thermo-induced phase transition and gelation, and rheological properties, with each other and the triblock controls (ABC, ACB, and CAB). It was found that the cloud point temperature (T_cp) of the pentablock terpolymer solution is related to the corresponding micelle conformation, which is dependent on the architecture of the polymer chain. Moreover, the BCACB pentablock terpolymer demonstrated enhanced gelation performance, exhibiting a broader gelation range in terms of both concentration and temperature as well as higher storage modulus (G′), compared to other pentablock and triblock counterparts.