Influence of architectural design on the thermoresponsive properties of pyrrolidone-based terpolymers

Abstract

This study investigated a new series of amphiphilic, thermoresponsive terpolymers based on pyrrolidone. The terpolymers feature similar compositions and molar masses but differ in their architectures, i.e., the position of comonomers along the polymer chain. All polymers were synthesised via reversible addition–fragmentation chain transfer (RAFT) polymerisation. The study focused on the polymers’ thermoresponsive behaviour in aqueous solutions. Specifically, the cloud point temperatures (T_cp) and self-assembly conformations, as well as the thermally induced sol–gel transitions, were investigated. The terpolymers exhibit a solvent isotropic effect and display different T_cps in deuterium oxide (D₂O) and deionised water (H₂O), as determined through turbidimetry measurements. The phase transitions were further analysed using temperature-variation ¹H NMR spectroscopy. Dynamic light scattering and transmission electron microscopy revealed that the triblock structure could self-assemble into micelles, whereas the statistical polymer could not. The micelle size varied depending on the pH. Visual testing and rheological studies showed how the polymer architecture influences thermoresponsive behaviour, with the BAC architecture exhibiting the widest gelation window. This research illustrates the importance of structure–property relationships and highlights the critical role of polymer architecture in their self-assembly and thermoresponsive properties.