The effect of comb architecture on complex coacervation. Issue 36 (4th September 2017)

• Record Type: Journal Article
• Authors: Johnston, Brandon M.; Johnston, Cameron W.; Letteri, Rachel A.; Lytle, Tyler K.; Sing, Charles E.; Emrick, Todd; Perry, Sarah L.
• Is Part Of: Organic & biomolecular chemistry. Volume 15:Issue 36(2017)
• Page Start: 7630
• Page End: 7642
• Publication Date: 2017-09-04
• Subjects: Chemistry, Organic -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1039/c7ob01314k
• Languages: English
• ISSNs: 1477-0520

Abstract

Abstract : Complex coacervation is a widely utilized technique for effecting phase separation, though predictive understanding of molecular-level details remains underdeveloped. Abstract : 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.