Pairs of ionic group dependence of the structure of a complex coacervate core micelle (C3M) in an aqueous solution was investigated using DLS, cryo-TEM, and SANS with a contrast matching technique and a detailed model analysis. Block copolyelectrolytes were prepared by introducing an ionic group (i.e., ammonium, guanidinium, carboxylate, and sulfonate) to poly(ethylene oxide-b-allyl glycidyl ether) (NPEO = 227 and NPAGE = 52), and C3Ms were formed by simple mixing of two oppositely-charged block copolyelectrolyte solutions with the exactly same degree of polymerization. All four C3Ms are spherical with narrow distribution of micelle dimension, and the cores are significantly swollen by water, resulting in relatively low brush density of PEO chains on the core surface. With the pair of strong polyelectrolytes, core radius and aggregation number increases, which reflects that the formation of complex coacervates are significantly sensitive to the pairs of ionic groups rather than simple charge pairing.

Complex coacervate core hydrogels were formed by simply mixing two oppositely charged polyether-based ABA triblock copolyelectrolyte solutions, where A blocks functionalized with either ammonium or sulfonate moieties form micellar cores and the cores are bridged by B block, poly(ethylene oxide). Small-angle X-ray/neutron scattering revealed the detailed hydrogel structure, including the micellar core dimension and characteristics, and the midblock conformation as a function of polymer and salt concentration. Furthermore, the relaxation process of the hydrogels where the micellar cores are disordered between 8 and 9.5 wt% was investigated by dynamic mechanical measurement. We observed that the time−salt superposition principle equipped with a sticky Rouse model captures the hydrogel relaxation dynamics. Varying the charged block length produces a significant change in the relaxation time, which is mainly attributed to the fact that the chain pullout process from the micellar cores is hindered by the thermodynamic energy barrier. The tunable viscoelastic characteristics of the complex coacervate hydrogels have important implications for applications as injectable and self-healable materials.

Molecular exchange dynamics between spherical complex coacervate core micelles (C3Ms) are documented using time-resolved small-angle neutron scattering measurements (TR-SANS), and the effects of salt concentration, type of charges, and core block polydispersity to the chain exchange are quantified. Isotopically labeled block copolyelectrolytes were prepared by postpolymerization modification of two nearly identical poly­(ethylene oxide-b-allyl glycidyl ether), one with normal and the other with deuterated PEO blocks (i.e., hPEO–PAGE and dPEO–PAGE). The observed rates at multiple salt concentrations are consolidated using time-salt superposition shift factors representing chain exchange rates and analyzed. Our comprehensive analytical relaxation function based on the sticky-Rouse model and the thermodynamic barrier for core block extraction successfully describes the molecular exchange kinetics between the isotopically labeled C3Ms. We believe this work provides fundamental design criteria for C3Ms with engineered chain exchange dynamics.

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.

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