Mixing polymers and polymer networks for topological adhesion

Adhesion between polymer networks is important for a wide range of medical applications. Established adhesion methods mostly focus on the chemical design of interfacial bonds to connect two polymer networks. By contrast, a recently developed adhesion method, called topological adhesion , uses an in situ gelated polymer network to connect two polymer networks through topological entanglement. The prerequisite of topological adhesion is the mixing of polymers and polymer networks. Understanding the mixing process and conditions will guide the design of topological adhesion systems to meet diverse adhesion requirements and situations. In this paper, we combine theoretical modeling and experiments to study the mixing of polymers with polymer networks. We take a thermodynamic approach to develop the mixing model and determine the concentration of mixing polymers under various material parameters of polymers and polymer networks. We first study two limiting cases in which the mixing polymer is one monomer long and infinitely long. We then provide a set of results on the general mixing cases. We further conduct polymer-hydrogel mixing experiments and characterize the mixing concentration in the hydrogel. The experiment results agree well with the theoretical prediction, except for cases with extremely low polymer concentrations. We finally discuss the design guidelines for enhancing the mixing of polymers and polymer networks for topological adhesion.