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Novel zwitterionic sulfobetaine polymers were synthesized, featuring alkene and alkyne groups embedded directly into the zwitterionic subunits. Alkene and alkyne versions of 1,3-propane sultone afforded access to functional zwitterionic methacrylates, which proved amenable to controlled free radical polymerization and copolymerization. These functional variants of polymer zwitterions exhibited desirable salt-responsive behavior characteristic of many polymer zwitterions, in which salt screened electrostatic interactions and resulted in droplet coalescence. Moreover, the presence of unsaturated groups in these polymers opens routes to facile chemistry at fluid–fluid interfaces and the preparation of robust polymer capsules.

Complex coacervation is a widely utilized technique for effecting phase separation, though predictive understanding of molecular-level details remains underdeveloped. Here, we couple coarse-grained Monte Carlo simulations with experimental efforts using a polypeptide-based model system to investigate how a comb-like architecture affects complex coacervation and coacervate stability. Specifically, the phase separation behavior of linear polycation-linear polyanion pairs was compared to that of comb polycation-linear polyanion and comb polycation-comb polyanion pairs. The comb architecture was found to mitigate cooperative interactions between oppositely charged polymers, as no discernible phase separation was observed for comb-comb pairs and complex coacervation of linear-linear pairs yielded stable coacervates at higher salt concentration than linear-comb pairs. This behavior was attributed to differences in counterion release by linear vs. comb polymers during polyeletrolyte complexation. Additionally, the comb polycation formed coacervates with both stereoregular poly(l-glutamate) and racemic poly(d,l-glutamate), whereas the linear polycation formed coacervates only with the racemic polyanion. In contrast, solid precipitates were obtained from mixtures of stereoregular poly(l-lysine) and poly(l-glutamate). Moreover, the formation of coacervates from cationic comb polymers incorporating up to ∼90% pendant zwitterionic groups demonstrated the potential for inclusion of comonomers to modulate the hydrophilicity and/or other properties of a coacervate-forming polymer. These results provide the first detailed investigation into the role of polymer architecture on complex coacervation using a chemically and architecturally well-defined model system, and highlight the need for additional research on this topic.