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Abstract Nematic monodomain liquid crystal elastomers (LCEs) undergo efficient temperature‐induced reversible shape‐shifting around the nematic‐isotropic transition temperature (Tni) due to the presence of the liquid‐crystalline order of mesogens. Usually, theTniof nematic LCEs is much higher than the human body temperature, and therefore LCEs are not often considered for biomedical applications. This study describes an LCE system where theTniis tuned by substitution of the rigid mesogens RM257 with a flexible backbone PEGDA250. By systematically substituting the RM257 with PEGDA250, theTniof LCEs was observed to decrease from 66°C to 23°C. A rate‐optimized LCE material was fabricated with 10 mol % rigid mesogens substituted with a flexible backbone that demonstratedTniat 32°C, in‐between the room temperature of 20°C and the body temperature of 37°C. TheTniallowed the programmed shape at room temperature, quick shape‐shifting upon exposure to body temperature, and before‐programmed shape when kept at body temperature. This LCE material displayed reversible length change of 23%, opacity change, and shape change between room temperature and body temperature.
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Shape Permanence in Diarylethene‐Functionalized Liquid‐Crystal Elastomers Facilitated by Thiol‐Anhydride Dynamic Chemistry
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.
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- Award ID(s):
- 1809841
- PAR ID:
- 10364030
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 61
- Issue:
- 11
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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