Ultra Rate‐Dependent Pressure Sensitive Adhesives Enabled by Soft Elasticity of Liquid Crystal Elastomers

• Published in: Advanced functional materials Vol. 34; no. 1
• Main Authors: Annapooranan, Raja, Suresh Jeyakumar, Sunil, J. Chambers, Robert, Long, Rong, Cai, Shengqiang
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2024
• Subjects: Adhesion; Adhesive strength; Adhesives; Dynamic mechanical analysis; Elastomers; Impact resistance; liquid crystal elastomer; Liquid crystals; Pressure dependence; Pressure sensitive adhesives; rate‐dependent adhesion; Stiffening; Strain; Temperature dependence; time‐temperature superposition; Viscoelasticity
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202309123

The fabrication of pressure sensitive adhesives (PSAs) using liquid crystal elastomers (LCEs), which are known for their excellent dissipation properties, is explored in this work. The adhesive properties of the PSAs are evaluated using the 180° peeling test at various conditions. The performance of the LCE adhesives is found to show significant rate and temperature dependence. When the adhesion energy is plotted against the rate, LCE shows an anomalously large power law exponent (n ≈ 1.17) compared to existing PSAs (n ≈ 0.1–0.6). The unusual rate sensitivity is hypothesized to originate from the synergy of soft elasticity and non‐linear viscoelasticity. The adhesive properties at various rates and temperatures are correlated to the results from dynamic mechanical analysis. Moreover, the large strain stiffening behavior of LCE under uniaxial tension reveals the distinctive advantages offered by LCE as adhesives. Time‐temperature superposition is used to obtain a master curve of adhesion energy that spans rates beyond typical experimental limits. The extreme rate dependence and the large strain stiffening of LCE yield a new category of adhesives that possess special properties, such as reversible adhesion and impact resistance, unlike traditional adhesives. In this work, a formulation of pressure sensitive adhesives using liquid crystal elastomers (LCE) is reported. Compared to traditional adhesives, LCEs exhibit anomalously high‐rate dependent adhesion, owing to soft elasticity and non‐linear viscoelasticity. Time‐temperature superposition and large strain behavior are used to elucidate the unique adhesive properties of LCE, which shows great potential for novel engineering applications.