Revealing Network Architecture Effects on Semi-Crystalline Polymer Networks

Semi-crystallinity enhances the stiffness, toughness, and thermal regulation of polymer network materials. Despite its known influence on crystallization in polymers, the relationship between network architecture and crystallinity remains poorly understood. We harness both experimental and computational thiol-ene click chemistry to uncover how network defects, strand lengths, and crosslinks drive crystallization behavior. By strategically selecting di-ene monomers, di-thiol chain extenders, and tetra-thiol crosslinkers, we synthesize a series of crosslinked networks spanning various crosslinking densities with base-degradable crosslinks, enabling us to isolate and analyze network strands. We then combine differential scanning calorimetry (DSC) and x-ray scattering to compare the phase behavior of intact polymer networks to their isolated strands. In parallel, we simulate analogous coarse-grained molecular dynamics reactions to generate detailed molecular snapshots of these materials. These complementary approaches reveal that systems with low crosslinking density and higher fractions of long dangling ends exhibit significantly larger extents of crystallinity. Therefore, we show that some defect formation can increase crystallinity and drive mechanical property enhancement.