Investigating oligo(ethylene glycol) methacrylate thermoresponsive copolymers

Abstract

Methacrylate-based polymers are frequently used in the development of thermoresponsive smart materials for biomedical applications. Among all the routes to such polymers, reversible addition fragmentation chain transfer (RAFT) copolymerisation is one of the most widely used. This paper reports the synthesis of thermoresponsive copolymers comprising oligo(ethylene glycol) methyl ether methacrylate with Mn of 300 (OEGMA300) and di(ethylene glycol) methyl ether methacrylate (DiEGMA). Polymers of molecular weight up to 100 kDA were obtained via RAFT polymerisation, mediated by a dithiobenzoate chain transfer agent (CTA) at 70 °C. An appropriate solvent, ratio of initiator to monomers, and minimum reaction polymerisation time were essential to provide optimum polymers. The synthesis of homogenous p(OEGMA300-co-DIEGMA) polymers with PDI of 1.1–1.2 was achieved in toluene with ≥10 h of reaction. Increasing the molecular weight of the p(OEGMA300-co-DiEGMA) polymers decreases the polydispersity index. p(OEGMA300-co-DiEGMA) polymers with Mw of 50,000 Da were successfully synthesised with lower critical solution temperatures (LCSTs) of 41.3 °C, 43.0 °C and >45 °C for OEGMA300:DiEGMA molar ratios of 2:8, 3:7 and 4:6, respectively. Further, the LCST was not found to be affected by the polymer molecular weight. The p(OEGMA300-co-DiEGMA) polymers showed no cytotoxicity to Caco-2 cells at a concentration of 1 mg mL−1, whereas a decrease of HDF cell viability by up to 26.5 % was seen. These polymers could be beneficial for several biomedical applications, such as developing formulations for temperature-triggered drug delivery.