Summary: Hydrolytic properties of thermoresponsive biopolymers with amphiphilic structures, γ-PGA-P, were investigated. Hydrolysis was monitored in terms of molecular weight changes using GPC and spectroscopic measurements. The hydrolytic degradation of γ-PGA-P was controlled by a change in the degree of propyl group conversion, reaction temperature, and/or reaction pH. The degradation was classified as the rapid elimination of propyl side chains and the moderate cleavage of peptide linkages in the backbone. Furthermore, hydrophobic environments established by the thermoresponsive coacervation of γ-PGA-P60 solutions inhibited hydrolytic degradation reactions. Inversely, hydrolytic degradations increased coacervation temperatures. Kinetic studies of hydrolytic reactions suggest that the degradation rate of γ-PGA-P60 solutions can be controlled by their thermoresponsivity. The hydrolysis reported here represents the first degradation rate controlled by thermoresponsive coacervation.
A schematic illustration of the hydrolytic mechanism of γ-PGA-P60.