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Liquid crystalline elastomers (LCEs) are soft materials that associate order and deformation. Upon deformation, mechanically induced changes order affect entropy and can produce a caloric output (elastocaloric). Elastocaloric effects in materials continue to be considered for functional use as solid state refrigerants. Prior elastocaloric investigations of LCEs and related materials have measured ≈2 °C temperature changes upon deformation (100% strain). Here, the elastocaloric response of LCEs is explored that are prepared with a subambient nematic to isotropic transition temperature. These materials are referred as “isotropic” liquid crystalline elastomers. The LCEs are prepared by a two‐step thiol‐Michael/thiol‐ene reaction. This polymer network chemistry enhances elastic recovery and reduces hysteresis compared to acrylate‐based chemistries. The LCEs exhibit appreciable elastocaloric temperature changes upon deformation and recovery (> ± 3 °C, total ΔTof 6 °C) to deformation driven by minimal force (<< 1 MPa). Notably, the strong association of deformation and order and the resulting temperature change attained at low force achieves a responsivity of 14 °C MPa−1which is seven times greater than natural rubber.
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Enhanced Electromechanical Output in Liquid Crystal Elastomers Prepared by Thiol‐ene Photopolymerization
Abstract The electrically‐directed, isothermal response of liquid crystal elastomers (LCEs) to an applied electric field is a compelling approach to realize spatially tailorable, sequence‐controllable, and high‐frequency deformation. The electromechanical response is facilitated by coating aligned LCEs with compliant electrodes. Upon application of an electric field, the electrodes attract and generate Maxwell stress. The directional difference in moduli for aligned LCEs produces directional deformation of the material and does not require mechanical bias or framing. Here, LCEs prepared from a newly reported thiol‐ene reaction are explored as DEAs with improved mechanical and dielectric properties. This report details that incorporating a difunctional liquid crystalline monomer composed of allyl ether functional groups reduces Young's modulus, increases the dielectric constant, and improves cyclic recovery compared to an analogous LCE prepared by thiol‐ene polymerization. Electrically‐induced, isothermal deformation of as much as 30% strain is reported. The facile chemistry and enhanced electromechanical response reported here may enable the functional integration of LCEs in applications such as robotics.
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- Award ID(s):
- 2105369
- PAR ID:
- 10530660
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 9
- Issue:
- 9
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/admt.202301970
