Shape Permanence in Diarylethene‐Functionalized Liquid‐Crystal Elastomers Facilitated by Thiol‐Anhydride Dynamic Chemistry. (25th January 2022)

• Record Type: Journal Article
• Authors: Hebner, Tayler S.; Podgórski, Maciej; Mavila, Sudheendran; White, Timothy J.; Bowman, Christopher N.
• Is Part Of: Angewandte Chemie. Volume 134:Number 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-25
• Subjects: Liquid Crystal Elastomers -- Covalent Adaptable Networks -- Shape Memory -- Diarylethene -- Robotics; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202116522
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Diarylethene‐functionalized liquid‐crystalline elastomers (DAE‐LCEs) containing thiol‐anhydride bonds were prepared and shown to undergo reversible, reprogrammable photoinduced actuation. Upon exposure to UV light, a monodomain DAE‐LCE generated 5.5 % strain. This photogenerated strain was demonstrated to be optically reversible over five cycles of alternating UV/Visible light exposure with minimal photochrome fatigue. The incorporation of thiol‐anhydride dynamic bonds allowed for retention of actuated states. Further, re‐programming of the nematic director was achieved by heating above the temperature for bond exchange to occur (70 °C) yet below the nematic‐to‐isotropic transition temperature (100 °C) such that order was maintained between mesogens. The observed thermal stability of each of the diarylethene isomers of over 72 h allowed for decoupling of photo‐induced processes and polymer network effects, showing that both polymer relaxation and back‐isomerization of the diarylethene contributed to LCE relaxation over a period of 12 hours after actuation unless bond exchange occurred. Abstract : Diarylethene is incorporated in liquid‐crystalline elastomers to generate phototropic deformation upon exposure to UV light. Thiol‐anhydride bonds within the network structure allow for alignment of the liquid crystalline elastomer and shape retention after initial deformation.