Abstract
Liquid crystal elastomers (LCEs) are important smart materials that can undergo reversible deformation in response to liquid crystal (LC) phase transitions. A low threshold temperature for LC phase transition is advantageous because the LCE material can be more conveniently actuated by the applied stimulus. In this work, we investigated the effect of a nonliquid crystal chain on the reduction of threshold temperature of the LC phase transition by linking a nonliquid crystal side chain, 4-methoxyphenyl-1-hexenyloxy (MOCH3), to the network backbone of a classical polysiloxane-based side-chain nematic LCE. The nematic–isotropic transition temperature (Tni) of the MOCH3 incorporated nematic LCE was lower than that of the normal nematic LCE without the incorporation of a nonliquid crystal chain by about 27 °C. Compared to the normal nematic LCE or its nanocomposite, the MOCH3 incorporated nematic LCE or its nanocomposite demonstrated more rapid thermo-actuated deformation or photo-actuated deformation, and can be actuated to attain full axial contraction at an obviously lowered temperature or by light with obviously lowered intensity, while the maximum contraction ratio basically did not vary. These research results indicate that some nonliquid crystal chains show potential for improving the characteristics and enhancing the application significance of LCE materials.
Highlights
As a unique type of smart polymer deformable materials, liquid crystal elastomers (LCEs) have been intensively studied in recent years due to their fascinating properties and potential applications.[1,2,3,4,5,6] LCEs are mesogen-containing networks formed by lightly crosslinked polymer chains, which show both the anisotropic orientation characteristic of liquid crystals (LCs) and the rubbery elasticity of polymer networks, and endow the PaperMost LCE materials are designed to be responsive by using heat or light stimuli
Based on the hydrosilylation of polyhydrogen methylsilxoane (PMHS) with MBB, MOCH3 and 11UB, the synthesized network of the modi ed LCE contained mesogens and nonliquid crystal side chains linked to the polymer backbone
The 2D-WAXS patterns of the four LCE materials exhibited consistent result that the locations of the wideangle re ection are orthogonal to the stretch directions of the materials, further con rmed the LC nematic-phase structure of LCE matrices, and that the mesogenic units were well aligned along the stretch direction
Summary
As a unique type of smart polymer deformable materials, liquid crystal elastomers (LCEs) have been intensively studied in recent years due to their fascinating properties and potential applications.[1,2,3,4,5,6] LCEs are mesogen-containing networks formed by lightly crosslinked polymer chains, which show both the anisotropic orientation characteristic of liquid crystals (LCs) and the rubbery elasticity of polymer networks, and endow the PaperMost LCE materials are designed to be responsive by using heat or light stimuli. The thermal-responsive LCEs perform reversible deformations related to the temperature-determined nematic–isotropic phase transition,[20] while the deformations of light-responsive LCE materials depend on either the molecular structure changes of the incorporated chromophores or the photo-thermal effect induced nematic–isotropic phase transition.[5,21,22,23,24,25] One typical type of light-responsive LCE materials takes advantage of the photo-thermal effect of thermal conductive llers to transform photon energy into heat which further induce the nematic–isotropic phase transition and actuate the LCE materials to deform.[10,17,18,26,27,28,29,30,31,32] The nematic– isotropic phase transition always occurs at a speci c temperature, which is the threshold temperature to produce the full actuation of a LCE material. The Tni can be in uenced by several factors, such as the crosslinking density,[33] the chemical structures of the mesogenic molecules and the network.[34,35,36] Some researchers' work indicated that the other possible ways to reduce the Tni should be by mixing two or more mesogenic molecules, or mixing the mesogenic molecules and nonliquid crystal molecules within the LCE network.[37,38]
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