Field-Based Simulations of Nanostructured Polyelectrolyte Gels

Nanostructured, responsive hydrogels composed of oppositely charged triblock copolymers with charged end-blocks and neutral, hydrophilic mid-blocks in aqueous solution were recently discovered. Due to electrostatic interactions, the end-blocks microphase separate and form physical cross-links that are bridged by the mid-blocks. Since these hydrogels are hydrophilic and have the ability to respond to a variety of stimuli including temperature and salt concentration, they are promising for a variety of biomedical applications including, but not limited to, drug delivery and tissue scaffolds. For such applications, there is a need to understand how to control the structure of the hydrogel. To this end, we use a new, efficient model along with self-consistent field theory to determine the structure as a function of polymer concentration and end-block fraction. After identifying numerous phases including a sphere phase, a hexagonally packed cylinder phase, a lamellar phase, and regions of phase coexistence, we determine how the polymer functionality can be tuned to manipulate the resulting phase diagram.