Pendant Side‐Chain Liquid Crystal Elastomers with Enhanced Viscoelastic Dissipation for Phase‐Dependent Pressure‐Sensitive Adhesion

ABSTRACT

Switchable pressure‐sensitive adhesives (PSAs) are important for sustainable manufacturing and advanced electronics packaging, but combining strong adhesion, on‐demand debonding, and long‐term reusability remains challenging. Here, we report an acrylate‐based liquid crystal elastomer (LCE) adhesive in which topology‐controlled viscoelastic dissipation enables strong and reversible adhesion switching. Pendant side‐chain mesogens are combined with chain‐transfer‐mediated radical polymerization to reduce crosslink density while preserving liquid‐crystalline order. This converts a glassy liquid‐crystal network into a soft PSA, lowering the glass transition temperature from 192°C to −11°C and the storage modulus from >10 ³ to <10 ^{− 1} MPa, satisfying the Dahlquist criterion for pressure‐sensitive adhesion. The LCE exhibits a broad dissipation window, with a peak loss factor of 1.86 and a loss factor maintained above 0.5 from 0 to 147°C. In the liquid‐crystalline phase, strong dissipation enables a peel strength of 1450 N m ^{− 1} . Upon transition to the isotropic phase, peel strength decreases to 9 N m ^{− 1} , achieving 99.4% adhesion loss and enabling rapid, residue‐free debonding. The adhesive retains performance over 50 bonding–debonding cycles, whereas commercial PSAs lose half of their adhesion strength after only five cycles. These findings establish topology‐controlled viscoelastic dissipation design strategy and provide a scalable LCE platform for reusable PSAs.