Relaxation Dynamics in Complex Coacervate Core Hydrogels: Charge Block Length Asymmetry*

Complex coacervate core hydrogels(C3Hs) are formed by mixing ABA triblock copolymer and oppositely charged A' counterparts, where complex coacervate core are bridged by hydrophilic B blocks in aqueous media. C3Hs have great potentials for sustained release drug delivery and additive manufacturing which is attributable to regulated hydrogel relaxation dynamics. In this study, we investigate the effect of chain length asymmetry on the hydrogel relaxation dynamics using dynamic mechanical analysis. C3Hs were prepared by mixing of ABA triblock copolymer and oppositely charged A'B diblock copolymer in salty water, which can distinguish the role of each charged polymers. We obtained that the relaxation times of C3Hs were considerably controlled by the average charge block length of two block copolyelectrolytes. Also, the radii of coacervate cores are reasonably regulated by the entropic penalty of core block stretching. The results are discussed in terms of the relaxation dynamics with current understanding of self-assembled triblock copolymer hydrogels.