Effects of Cross-Linking Density on Interfacial Polymerization and Scaffold Formation in Functionalized Polymer Beads

Particles that are functionalized with complementary groups, which undergo bimolecular or co-initiation reactions via contact between particles, may act as blood-clotting mimics and find use in self-healing systems. Here, we show that modifying the cross-linker identity and density during particle synthesis affords polymer beads that exhibit differences in their ability to take up the monomer. The beads are functionalized with complementary co-initiator groups based on benzoyl peroxide or dimethylaniline, which, when brought into physical contact, co-initiate polymerization of the surrounding monomers. During polymerization, the beads take up the liquid monomer and polymerization occurs at the interface of the complementary-functionalized beads to afford a scaffold composed of beads and new polymer. However, the robustness of the scaffold is dependent on the identity and density of the crosslinker that is incorporated into the bead matrix. Beads synthesized with lower degrees of crosslinking exhibit higher swelling capabilities and yield scaffolds with more beads and polymer connected to each other following interfacial polymerization. The findings presented here provide insight into how polymer bead properties affect interfacial reactions and will guide the design of new self-healing motifs.