(375b) Strong Effects of Charge and Salt on Polymersome Membrane Elasticity

Assemblies of charged, amphiphilic diblock copolymers have been shown to undergo phase transitions from spherical micelles to worm micelles to bilayer vesicles ? or polymersomes ? based on solution pH and salt concentration. Using micromanipulation techniques, we show that the presence of salts increases the charged membrane's stiffness compared to the neutral membrane. The elastic properties of neutral, crosslinkable diblock copolymer membranes have been characterized in the past to show a strong dependence on copolymer molecular weight and the extent of cross-linking in the bilayer. Similarly, we investigate whether an increase in membrane stiffness is dependent on the concentration or the valency of the cation. By blending charged and neutral diblock copolymers, we also determine the effect of a changing charged copolymer concentration on the elasticity of the membrane.