Liquid crystalline elastomers (LCEs) are a compelling class of shape-changing materials due to their intrinsic response to stimulus. By incorporating liquid crystalline units (mesogens) covalently into the network structure, the polymer retains anisotropic liquid crystalline phases that are disrupted upon exposure to stimulus such as heat or light. Since LCEs combine properties of both polymers and liquid crystals, both mesogenic properties and polymer network structure impact deformation behavior and need to be considered in the design of LCEs as stimuli-responsive actuators.<br/>In this work, a method for tuning LCE response based on mesogenic structure was first investigated, finding that using a mesogen with reduced aromatic content to decrease the extent of π-π interactions results in more efficient disruption of order by heat or light. The coupling of liquid crystalline order with crosslinking conditions was analyzed, finding that the method by which the LCE is macroscopically aligned affects phase behavior of the polymer due to the balance between elastic and nematic energy. Finally, using the knowledge gained in the first two studies, a complex photo-responsive LCE actuator was designed to have stable photochemical response using diarylethene as the photoisomerizable moiety. Dynamic covalent chemistry is incorporated using thiol-anhydride functionalized monomers, introducing potential for (re)programmable alignment and shape retention in deformed states. Combining the various elements of this work, an LCE was designed with phase behavior such that dynamic chemistry and photo-actuation are each activated in distinct steps using orthogonal stimuli, resulting in (re)programmable deformation modes, spatiotemporal control of actuation using light, and shape retention in actuated states using heat in a single LCE.

Tuning fundamental properties in liquid crystalline elastomers for design of complex and reprogrammable actuation

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.