The Fabrication And Appliction Of Liquid Crystal Elastomer Fibers

Liquid crystal elastomers are stimulus-responsive materials that received much attention in recent years.Under external stimuli,the mesogens within the elastomers can be transformed from liquid crystal phase to isotropic phase,enabling liquid crystal elastomers to exhibit excellent responsive deformation at the macroscopic scale.Fibers play an important role in modern industry and human daily life,and how to construct intelligent fibers that can respond to external stimuli is becoming an increasing focus of the materials science community.Liquid crystal elastomer fibers,which possess the excellent stimulus responsiveness of liquid crystal elastomers and the flexibility and processability of fibers,have shown broad application prospects in the fields of soft actuators,artificial muscles,and smart fabrics.At present,researchers have made a series of explorations in the preparation and application of liquid crystal elastomer fibers,but there are still some bottlenecks to be solved: utilizing liquid crystal elastomer fibers to construct multi-dimensional structures has not been achieved yet;the deformation mode of liquid crystal elastomer fibers only contains contraction and bending,which limits its practical application;liquid crystal elastomer fibers tend to only respond to one single kind of stimulus in the undoped state.In this dissertation,we propose solutions to these problems by constructing complex3 D actuators through biomimetic strategies,by twisting the fibers to obtain rotational deformation,and by constructing hollow fibers to endow the fibers with pressure-thermal dual stimuli responsiveness.This dissertation focuses on the fabrication and application of liquid crystal elastomer fibers and consists of three parts as follows.(1)The uniaxially aligned ultra-long liquid crystal elastomer fibers are prepared by dry spinning method,and a biomimetic construction strategy is proposed to construct an artificial cardiac muscle by arranging the liquid crystal elastomer fibers in a helical and circular spatial structure on a flexible substrate,by mimicking the arrangement of real cardiac muscle fibers in the heart.The artificial cardiac muscle can produce a similar deformation as the real heart,and twist while contracting to achieve pumping function.(2)Combining the template method and fiber twisting technology,we induced twist orientation into fibers to obtain liquid crystal elastomer twist fibers.The fibers can produce rotational deformation and output torsional force under thermal stimulus.The liquid crystal elastomer twist fibers can rotate weights,so it can be utilized as a rotating microengine to rotate the rotor in an electricity-generating device and convert thermal energy into electrical energy.(3)Employing the template fabrication method,the liquid crystal elastomer hollow fibers with cavity are obtained by evaporating the solvent gradually during the crosslinking process.By controlling the evaporation rate of the solvent at different positions of the template,liquid crystal elastomer bamboos can be obtained.Both the hollow fibers and bamboos can be used to construct pneumatic artificial muscles,which have both pressure and thermal responsiveness and exhibit excellent deformation capability.