Lewis Pairs as Highly Tunable Dynamic Cross-Links in Transient Polymer Networks

Classical Lewis pairs (LPs) between unhindered electron-poor Lewis acids (LAs) and electron-rich Lewis bases (LBs) present an overlooked motif with tremendous potential as dynamic cross-links in transient polymer networks (TPNs) for self-healing and stimuli-responsive applications. We demonstrate that simple and intuitive matching of weak/strong organoborane LA and amine LB pairs offers access to a large set of binding equilibrium constants, K_eq, that span ∼6 orders and dissociation rate constants, k_diss, that span ∼7 orders of magnitude. The implementation in polystyrene (PS)/polydimethylsiloxane (PDMS) blends results in dynamically cross-linked networks with bulk thermomechanical properties that are directly correlated with the strength and kinetic parameters for the LP interactions. The LP dynamic cross-link design is highly versatile and broadly applicable to different polymer architectures as demonstrated in the formation of reprocessable elastomers from Lewis base-decorated high molecular weight PDMS in combination with Lewis acid-decorated PS when reinforced with fumed silica as a filler.