Domain Formation in Charged Polymer Vesicles

Microphase separation can occur on a polymersome membrane surface. The phase behavior depends on the mixture of charged and uncharged diblock copolymers and the salt concentration in solution. Using coarse-grained molecular dynamics simulations, we evaluate the elastic properties of mixed charged and uncharged diblock copolymer membranes as a function of charged polymer concentration for the case of divalent counterions in solution. We find that both the area elastic modulus and bending modulus increase with increasing charged copolymer concentration. We find that the membrane thickness decreases and the membrane overlap increases with increasing charged copolymer concentration. We next perform large-scale simulations of a nearly 30 nm polymersome and characterize the growth of domains over a 0.5 μs simulation time. We characterize the size, shape, and surface topology of the domains as they grow. These results add insight into the underlying mechanisms guiding the growth of domains in both synthetic and living cells.