Multi-Stimuli Responsive Carbon Nanotube Incorporated Polysiloxane Azobenzene Liquid Crystalline Elastomer Composites

In this work, aiming to combine thermal-induced LC-to-isotropic phase transition effect, azobenzene's trans-cis tautomerization effect and the photothermal effect into one liquid crystalline elastomer (LCE) system to prepare a heat/UV/near-infrared(NIR) triple-stimuli-responsive LCE material, we design and synthesize a polysiloxane-based side-chain side-on azobenzene-containing LCE matrix embedded with 1 wt % single-walled carbon nanotubes, through Finkelmann's two-step cross-linking process coupled with a uniaxial stretching technique. The multistimuli responsive behaviors of this LCE/CNT composite film are investigated under different external stimuli (heat, UV, NIR). The composite film can realize a reversible deformation between contraction and extension under heating/cooling cycles. Moreover, the composite film can perform an impressive three-dimensional deformation (bending) under UV-light irradiation. On the contrary, long wavelength light (NIR laser) forces the composite film into shrinking instead of bending. Most importantly, the shape transformations (three-dimensional bending vs two-dimensional shrinking) of this novel shape memory material can be tuned by the light wavelength (UV vs NIR), which might endow this LCE material with potential applications in control devices and logic gate devices, etc.