UC San Diego

Elastomeric materials, characterized by their elasticity and energy dissipation capabilities, are crucial in everyday life. Over the years, the development of elastomers with novel properties is driven by the growing demand for materials that can meet the increasingly complex and specific requirements in automotive, aerospace, medical, structural and industrial applications and enable new applications such as soft robotics and flexible electronics. Liquid crystal elastomer is one such material system that combines liquid crystals with rubbery polymers, which gave rise to several unique properties such as anisotropic elasticity, stimuli responsiveness and actuation, energy dissipation, photoelasticity and reversible adhesion. Since materials need to withstand multiple cycles of mechanical loading and exposure to thermal fields in real world applications, it is important to understand the rate and temperature dependent properties of liquid crystal elastomers, which will result in the development of robust materials and reliable engineering structures.

In this dissertation, we first explore the rate and temperature dependent fracture properties of liquid crystal elastomers and develop predictions of the temperature of self-rupture for various geometries. Secondly, we develop an interpenetrating network strategy to improve the high temperature fracture and fatigue properties of liquid crystal elastomers, while preserving their actuation properties. Then, we develop a pressure sensitive adhesive using liquid crystal elastomers and explore the ultra-high rate dependence of adhesion energy. Finally, we study the enhanced adhesion of liquid crystal elastomers on various rough surfaces. We hope that the understanding of the fracture and adhesive properties of liquid crystal elastomers and the strategies developed to further improve these properties using materials chemistry will translate to real world in solving critical challenges in medical technology, robotics, automotive, aerospace and industrial applications