Dynamic Covalent Polymer Networks of Silicone Elastomers via Organoborane Lewis-Pairs

Dynamic covalent polymer networks (DCPNs) have been developed in recent years to offer distinctive mechanical properties and shape responsiveness in covalently cured polymer materials, thereby bestowing them with desirable characteristics such as self-healing and recyclability. To achieve these desirable properties, dynamic polymers incorporate reversible covalent bonds that enable shape morphing without causing irreversible chemical degradation of the network structure. Lewis pairs (LP), forming coordinate covalent bonds, sometimes referred to as dative covalent bonds, exhibit a broad range of bond dissociation rates and energies, making them inherently interesting for designing DCPNs. However, LPs have been relatively unexplored as polymer building blocks. Here, we present a straightforward approach to prepare LP-based polymers based on archetypical nitrogen-borane adducts with an organoborane-functionalized polydimethylsiloxane combined with commercially available Lewis base (LB) polymers. The dynamic behavior of the organoborane-functionalized system and LB polymers is investigated, demonstrating tunable reversibility in cured elastomers. The excess of LB facilitates rapid recapture and reformation of the covalent network, contributing to the system's reversible and self-healing nature. Notably, the system allows easy mixing of different LB polymers, enabling the creation of tuning the system, and hence organoborane-based LPs are demonstrated to be a promising building block for tunable DCPNs.