| Photo-induced deformation polymeric materials have been a research focus recently due to the unique merits of light:clean, safe, remote controllable and transient. Among those materials, crosslinked liquid crystalline polymers (CLCPs) stand out as a hotpot in recent years due to the following two reasons:(1) Rubber elasticity of polymer network is combined with orientation of liquid crystals to provide CLCPs with some distinctive properties;(2) CLCPs can directly convert light into mechanical energy. For example, CLCP films contain azobenzene can undergo bending and unbending behaviors upon irradiation by UV light and visible light respectively. Through properly design, CLCPs can even realize complex motions like stretching, bending, creeping and rolling. Therefore, various kinds of flexible actuators driven by light may be fabricated for wide applications in artificial muscles, micro-machinery, micro-pump, micro-valve, and etc. On the other hand, traditional mechanical rubbing technique utilized to achieve liquid-crystalline (LC) orientation may cause damage to materials due to the existence of impurities or electrostatic accumulation. Besides, CLCPs based materials also suffer from defects such as monotonous performance, poor mechanical strength, and size limitations, which will interfere with their further applications. Herein, we use CNT sheets as template to align the LC mesogens in the process of the fabrication of CLCP/CNT composite films. The prepared composite films have favorable mechanical, electrical and photodeformable properties. Furthermore, reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to synthesize the block copolymer PEO48-b-PAZO and research its’ deformed behavior.Firstly, two monomers A11AB6and A9Bz9, and the crosslinker C9A were prepared, a CNT array was grown on silicon by chemical vapor deposition, uniform CNT sheets were pulled out of the array by dry spinning and stabilized on glass substrates, the CLCP/CNT composite film was obtained after in situ photopolymerization. It was found that the aligned nanostructure of the CNT sheet could effectively orient the CLCP mesogens along the length of the CNTs without using any other aligning layer. On the other hand, we discover a direct photoactuation of a deformable CLCP/CNT composite film. The CLCP/CNT composite film exhibited much higher mechanical strength of31.2MPa and high electrical conductivity of270S/cm which has not been realized for the other CLCP materials. As a result of the combined properties, the CLCP/CNT composite film could be widely used as many applications.Reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to synthesize the block copolymer PEO-b-PAZO. Firstly, the synthesized reactive monomer was characterized by1HNMR, DSC and POM analysis demonstrate that it have property of liquid crystal in a certain temperature range; We developed a chemical crosslinking method of a reactive block copolymer precursors contaning polymethacrylate bearing N-hydroxysuccinimide carboxylate substituted azo group and poly(ethylene oxide) PEO with a difunctional amine. The PEO-b-PAZO was characterized by1HNMR, DSC, POM and SAXS analysis demonstrate that it have property of smectic-A liquid crystal; On one hand, the introduction of a soft PEO can supply enough free volume for photoisomerization and phase transition of AZO, which enables us to obtain more excellent photoresponsive CLCPs. On the other hand, such homogeneous polymers were proved to be good precursors for liquid crystalline polymer networks. Therefore, the reactive block copolymers are advantageous for being processed into diverse shapes and dimensions through melt spinning or solution casting. Herein, we developed a facile method to obtain CLCP fiber and film composed of the block copolymer. We also show the anisotropic bending of CLCP fiber and a precise directional control of bending in a CLCP film induced by UV light. |
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