Temperature- and time-dependent evolution of hydrogel network formed by thermoresponsive BCACB pentablock terpolymers: Effect of composition

Three thermoresponsive BCACB pentablock terpolymers, in which A, B, and C blocks were composed of hydrophilic oligo (ethylene glycol) methyl ether methacrylate (average molar mass = 300 g/mol, OEGMA300), hydrophobic n-butyl methacrylate (BuMA), and less-hydrophilic di(ethylene glycol) methyl ether methacrylate (DEGMA), respectively, were synthesised via one-pot group transfer polymerisation (GTP) with varied chemical compositions. In addition to the thermoresponsive behaviour, a time-dependent evolution was also observed in both microscopic structure and macroscopic performance of the thermo-induced hydrogels formed by these terpolymers. Combined analysis using time-resolved small angle X-ray scattering (TR-SAXS) and rheometry reveals that achieving a balanced ratio of hydrophobic and hydrophilic content is critical for configuring hydrogel networks with optimal performance and stability. Specifically, an excessive hydrophobic content leads to a gradual loss of network storage modulus (G′) over time, while an overwhelming hydrophilic content diminishes the formation of stable elastic-active intermicellar correlations, resulting in the lowest G’.