Publication Date

2017

Journal or Book Title

Organic & Biomolecular Chemistry

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.

DOI

10.1039/C7OB01314K

Comments

Org. Biomol. Chem., 2017, Accepted Manuscript

License

UMass Amherst Open Access Policy

Funder

B.M.J. acknowledges support from the University of Massachusetts, Amherst Commonwealth Honors College Fellowship, C.E.S. acknowledges support from NSF CAREER Award DMR-1654158 and use of the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant ACI-1053575. R.A.L. and T.E. acknowledge financial support from the National Science Foundation (NSF CBET 1403742) and facilities support from the Materials Research Science and Engineering Center (MRSEC DMR-0820506) on Polymers at the University of Massachusetts.

Combs SI - Final.pdf (555 kB)
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