Preparation And Electro-Responsive Properties Of Carbon/Liquid Crystal Elastomer Composites

Flexible devices have become the focus of research in many fields because of the outstanding advantages including good flexibility,large shape variation,and integration.As a typical stimulation-response bidirectional shape memory material,liquid crystal elastomer(LCE)has been widely employed to fabricate flexible actuators,sensors,soft robotics,and other flexible devices.Among various external stimuli,electricity,as the most common energy source in human life,has the advantages of fast,clean,huge energy,and high controllable precision.However,there are relatively limited researches on electrical stimuli-responsive liquid crystal elastomers.As a conductive material with outstanding properties,carbon nanomaterials are often added into polymer systems as conductive fillers to improve the conductivity of polymer materials.In this paper,we have designed and prepared carbon material/liquid crystal elastomer composites,investigate their mechanical properties and electrical stimulus-responsive behavior,and explore their applications in electrodeformation actuators and flexible strain sensors.The main research contents are as follows:(1)Preparation of pure LCE film and carbon material/LCE composite film.Firstly,different preparation methods are used to find out the optimized film preparation process.A variety of liquid crystal elastomer films are prepared by adjusting the mole ratio of crosslinkers,chain extenders and liquid crystal monomers.Differential scanning calorimeter(DSC)is used to characterize the thermal properties,and the most appropriate mole ratio is selected for the preparation of LCE composite films.Finally,carbon materials such as carbon nanotubes and carbon fibers are physically doped into the LCE systems with different mass concentrations to obtain a series of carbon materials/LCE composite films.Their basic properties are characterized by Fourier transform infrared spectroscopy(FT-IR)and thermogravimetry analysis(TGA).(2)Exploration of electro-induced deformation and sensing properties of carbon nanotubes/liquid crystal elastomers(CNT/LCE)with different mass concentrations.Firstly,the thermal,surface morphology and orientation of CNT/LCE composite films are characterized by DSC,SEM and SAXS.The results show that the CNT/LCE composite films have good orientation,and the mechanical properties have been significantly improved.The electrothermal conversion efficiency and electro-induced deformation effect of the composite film are investigated by measuring the surface temperature and shape changes of the composite film after applying different voltages.Finally,CNT/LCE composite films with different mass concentrations are used for the preparation of sensors.The stability,durability and sensing sensitivity of the sensors are further investigated.The experimental results show that RM257-CNT-12 film has the most stable sensing performance and a large sensing strain range.(3)Exploration of electronic deformation and sensing properties of carbon fibers/liquid crystal elastomers(CF/LCE)with different mass concentrations.Firstly,DSC,SEM,SAXS and high resistance meter were used to explore the thermal,mechanical,orientation,electrical conductivities of CF/LCE films.Then,the electrothermal conversion efficiency and electro-induced deformation of CF/LCE under different voltage conditions are further studied.Finally,the CF/LCE composite films are used for the fabrication of the sensor,and the sensor stability is tested with different tensile speeds and tensile degrees.The results show that RM257-CF-9has the best sensor stability,and it can output repeated sensor signals even after 100 cycles.The sensor has high sensitivity with a G_F of 261.96,which is beneficial for the detection of small strain.These data imply the application prospect of CF/LCE sensor in human motion monitoring.