Cobalt-Catalyzed Chain Transfer Polymerization Enables Soft Methacrylate Nematic Elastomers for Switchable Pressure-Sensitive Adhesion

Abstract Liquid crystal elastomers (LCEs) exhibit unique viscoelastic behavior arising from their reversible liquid-crystalline ordering, making them attractive candidates for switchable pressure-sensitive adhesives (PSAs). However, crosslinked methacrylate-based liquid crystal polymer networks are inherently rigid, resulting in elevated glass transition temperatures (Tg) and storage moduli (E′) that limit their adhesive performance. Here, we demonstrate that catalytic chain-transfer polymerization provides an effective strategy for engineering soft methacrylate nematic elastomers through systematic control of network architecture. Incorporation of ppm-level concentrations of bis(boron difluorodimethylglyoximate)cobalt(II) (CoBF) during photopolymerization reduced the effective crosslink density and increased the molecular weight between crosslinks, resulting in substantial decreases in Tg and E′ while preserving nematic order. Dynamic mechanical analysis revealed that increasing CoBF concentration enhanced viscoelastic dissipation and broadened the accessible nematic temperature range. To further optimize the rheological properties for pressure-sensitive adhesion, monofunctional methacrylate monomers and a flexible difunctional methacrylate crosslinker were incorporated into the network. The optimized formulation exhibited a Tg near 0 °C, a room-temperature storage modulus of approximately 0.3 MPa, and high damping behavior, approaching the Dahlquist criterion for pressure-sensitive adhesion. Thus, the resulting nematic elastomers exhibited strong tack, peel, and lap-shear adhesion in the nematic state together with rapid, reversible, and residue-free debonding upon heating above the nematic-to-isotropic transition temperature. These results establish catalytic chain transfer as a versatile platform for tuning the structure–property relationships of methacrylate nematic elastomers and provide a scalable route toward reusable and debond-on-demand adhesive materials.