Tuning Structure and Dynamics of Structured Ionic Block Copolymers Assemblies in Solutions

Tethering blocks with distinctive characteristics to an ionizable polymer allows the incorporation of multiple characteristics into one macromolecule, enabling the design of materials for targeted applications. These blocks are often in the high segregation limit, and form well defined assemblies in solutions. Changing the electrostatic environment of these polymers either through solvent modifications or through directly modulating the electrostatic interactions, affects the structure and dynamics of these polymers. Using neutron techniques and molecular dynamics simulations, the current study probes micelles formed by ABCBA pentablock copolymer, as a model system, to probe the effects of changing the electrostatic environment on the structure and dynamics of their assemblies in solutions. The polymer that consists of poly(t-butyl-styrene) (A), poly(ethylene-r-propylene) (B), and poly(styrene-r-styrene sulfonate) (C) was desoved in cycloheane, formiing core-shell miclles. Electrostatics' impact on the structure will be discussed as the sulfonation leveled of the center block varies from the ionomer to the polyelectrolyte regime as different amounts of THF were added to the system. We find that the core-shell spherical micelles dominate the structure in all systems studies, however molecular conformation is affected. Further insight into the effects of electrostatics as extracted from MD simulations will be presented.