Preparation And Performance Study Of Intrinsic Carbon Nanotube Liquid Crystal Elastomer

Liquid crystal elastomers(LCEs),as an emerging smart polymer material,exhibit large and reversible deformations under external stimuli(heat,light,chemical substances,electricity or magnetic fields,etc.).It has essential application value in artificial muscles,flexible robots,smart surfaces,biomedicine and other intelligent fields.However,due to its poor mechanical strength,low actuation stress,and single response mode(mainly thermal response),it has always stayed in the research stage.Therefore,how to achieve the preparation of LCE actuator with excellent mechanical properties and multiple response functions through material design and structural optimization is a problem that needs to be solved urgently.Near-infrared light response has attractive characteristics such as strong penetrating power,remote control,local drive,and harmlessness,so it has been widely used in stimulus responses.Carbon nanotubes(CNTs)are widely used in the research of LCEs because of their high mechanical strength(1 TPa),high thermal conductivity(up to 6000 W m^-1k^-1),and good light absorption property.However,CNTs easily agglomerate and difficulty in alignment.As a result,the load cannot be effectively transferred between CNTs and between CNTs and LCE matrix,and in addition,the light energy cannot be efficiently converted into heat energy.Based on the above problems,this topic prepared LCE by adjusting its topological structure,the surface morphology,phase behavior,thermal stability,and mechanical properties were explored.Then functionalized multi-walled carbon nanotubes(F-MWNT)were added to the LCE to prepare intrinsic LCE and F-MWNT/LCE nanocomposites respectively,and their internal structure,phase transition behavior,mechanical properties,thermal actuation properties,light actuation properties,etc.were explored.Preparation and performance study of temperature-responsive liquid crystal elastomers.This work chose 1,4?bis?[4?(6?acryloyloxyhexyloxy)benzoyl-oxy]?2?methylbenzene(RM82)as LC core,pentaerythritol Tetra(3-mercaptopropionate)(PETMP)as the crosslinking agent,1,10-Decanedithiol(DT)as the spacer to fabricate the LCE matrix.By adjusting sulfhydryl groups'ratio of PETMP and DT,the influence on the matrix structure was studied.The prepared liquid crystal elastomer(RM82-PT₀-DT₁₀)exhibits a nematic schlieren texture,and its liquid crystal range is from-17 to 86?.With the clearing point decreases.The LCE has high thermal stability,and the decompositionincrease of crosslinking agent,the temperature range is between 316-527?.Among them,RM82-PT₀-DT₁₀,RM82-PT₁-DT₉,and RM82-PT₂-DT₈have the best thermal stability.RM82-PT₁-DT₉has a higher elongation at break(The elongation at the break of the polydomain sample is 305%,while that of the monodomain sample is 127%).In summary,LCE'structure can be controlled by adjusting the internal composition,and the intermolecular force is an important factor that affects the performance of the LCE.Preparation and performance study of intrinsic LCE and F-MWNT/LCE nanocomposite.In order to improve the dispersion of carbon nanotubes in liquid crystal elastomers and realize the multiple response characteristics of LCE materials to stimuli such as light and heat,carbon nanotubes(0.1 wt%)with double bonds at the ends were introduced into the LCE system.The one-pot method combined with the two-step cross-linking reaction to prepare the intrinsic LCE.The results show that many"strip structures"with the diameter of about 600 nm and good alignment were formed in the intrinsic LCE.Among intrinsic LCE and F-MWNT/LCE nanocomposites,MWNT-AC/LCE has the best overall performance,with an average tensile strength of 13.87 MPa,which is 4.2 times higher than LCE.Under infrared laser,the actuation stress reached 1.66 MPa.This is mainly due to the covalent cross-linking and?-?conjugation that together enhance the interfacial adhesion between the carbon nanotubes and the liquid crystal elastomer,and improve the dispersion of the carbon nanotubes in the LCE.Under the same infrared laser density irradiation,the MWNT-AC/LCE reaches the phase transition temperature within 6 s,and the surface temperature of the sample is the highest,which is attributed to the good dispersion and alignment in the matrix,which improves its photothermal conversion efficiency.By preparing multilayer actuators and serpentine actuators,multiple responses of LCE are realized.In addition,this method provides new ideas for the design and preparation of new high-performance smart materials,and is expected to be applied to bionic devices such as artificial muscles and smart grippers.