Effect of Charged Block Length Asymmetry on Complex Coacervate Core Hydrogels

For complex coacervate core hydrogels (C3Hs) formed by mixing two oppositely charged block copolymer solutions, the influence of asymmetry in charged block length, arising from pairing blocks of unequal size, was investigated using small-angle X-ray scattering and rheology. Well-defined C3Hs can be prepared from block copolymers with asymmetric charged block lengths, in which one charged block is shorter or longer than its oppositely charged counterpart. Systematic variation of the charged block length in diblock copolymers, while keeping the triblock constant, revealed concurrent changes in micellar core dimension and hydrogel relaxation time. Free-energy analysis indicated that short and long blocks adopt distinct conformations within the cores, collectively determining micellar structure. Moreover, the relaxation time scaled proportionally with the average charged block length, ⟨ N end ⟩, suggesting that the viscosity of the hydrated coacervate core plays a dominant role in controlling relaxation behavior. These findings provide a framework for optimizing C3Hs with tunable viscoelastic properties for biomedical applications.