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, Keq, that span ∼6 orders
and dissociation rate constants, kdiss, 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.