Co‐assembly behavior of oppositely charged thermoresponsive elastin‐like polypeptide block copolymers

The formation of complex coacervate core micelles (C3Ms) was observed by mixing two oppositely charged elastin‐like polypeptides (ELP)‐based diblock copolymers, each composed of a neutral and a charged moiety. The physical properties of C3Ms as a function of pH, temperature, and salt concentration were analyzed by UV–visible spectrometry, dynamic light scattering (DLS), 1H NMR, and small angle X‐ray scattering (SAXS). In distilled water (or low salt conditions), below the transition temperature (Tt), ELP mixtures induced the C3Ms with a complex coacervate core and a neutral corona; meanwhile, above the Tt, they aggregated by the hydrophobic interaction among the neutral coronas. However, as the salt concentration increased, the induced C3Ms gradually dissociated; while above the critical micellar temperature (CMT) and critical salt concentration (CSC), inverted hydrophobic core micelles surrounded by the charged blocks were created. Based on these results, we demonstrate that the co‐assembly behavior of two oppositely charged diblock ELPs is harnessed by the salt concentration and temperature.