Influence of Mesh Size on the Structure and Properties of Polyelectrolyte Complex/Covalent IPN Hydrogels

Crosslinking of covalently crosslinkable precursors interspersed within PEC networks has emerged as an effective strategy to create PEC/covalent IPN hydrogels that feature distinct enhancements in microstructural diversity, shear and tensile strength, and swelling behaviors. In this presentation, we will demonstrate the variation of the precursor chain length as an approach to tune the microstructure and the mechanical properties of PEC/covalent IPN hydrogels without changing polymer concentrations. Before crosslinking, the chain length of the precursors correlates inversely with the shear moduli of PEC hydrogel. Correspondingly, the largest improvements in the shear moduli are noted in the crosslinked PEC/covalent IPN hydrogels composed of the shortest precursors. The presence of the precursor chains will be argued to affect the connectivity of the PEC network, with the precursor chain length and concentration both affecting the fraction of elastically-effective bridging strands in the PEC network. These hypotheses will be critically evaluated in the context of theories describing the rheology of transient networks to establish design rules for PEC/covalent IPN hydrogels with prescribed structures and properties.