The Regulation Of Microstructures And Investigation On Electromechanical Properties Of Photocurable Polyurethane Dielectric Elastomer Actuators

After decades of research,polymer-based dielectric elastomers have shown amazing potential in the fields of biomimetic artificial muscles,flexible intelligent robots,energy collectors and sensors,but how to balance the relationship between dielectric properties and mechanical properties of dielectric elastomers,so as to prepare high-performance dielectric elastomer actuators with excellent comprehensive electro-mechanical properties to meet the actual demand is still a key problem.In this paper,polyurethane materials as the main research object,starting from the topological structure design of molecular chain,the regulation of chain end group to trigger local microphase separation,at the same time with the introduction of a push and pull charge effect of polar groups,the preparation of different crosslinked network structure of high performance polyurethane based dielectric elastomer materials.Furthermore,the three-dimensional structure of dielectric elastomer driver was designed and regulated by ink precision direct writing 3D printing technology(DIW),and the Layer-by-layer(LBL)double-layer printing structure of Janus dielectric elastomer driver was prepared.The effects of molecular chain structure,interface push-pull charge polarization effect and LBL structure on the driving properties of final devices are discussed in detail,aiming to solve the problem that it is difficult for polyurethane dielectric elastomers to take into account both low elastic modulus and high dielectric constant.The achievements of this paper are as follows:(1)PUA photocured films with different crosslinked network structures were prepared.By testing the relevant properties of the film,it is found that the Type II network structure with locally concentrated crosslinking points has a long molecular chain,which leads to the self-entanglement of the linear molecular chain and the formation of microphase separation in the cross-linked region,which improves the dielectric constant of the material,so that the cured PUA film can obtain a higher dielectric constant without significantly improving the retention modulus.The electro-mechanical properties are relatively balanced.The results show that the maximum driving strain of PUA5 film with typeⅡlocal cross-linked network structure can reach 13.88%when the driving electric field intensity is 45.41V/μm.(2)Based on the work in the previous chapter,polyurethane styrene butadiene rubber(BSPU)and polyurethane nitrile butadiene rubber(BNPU)dielectric elastomers with different crosslinking structures and side base effects were prepared.By comparison,it is found that the driving factor of BNPU1 with the highest cyanogroup content is about 13.24 due to the high Young’s modulus,while that of BNPU3 film with low cyanogroup content is 14.22,which is slightly higher than that of BNPU1 film.For BSPU films,the final driving factor of BSPU1 with lower benzene content is 17.73,which is significantly higher than that of other groups of samples.The incremental drive bending Angle of BNPU3 is about 28.8°@18 V/μm,and the incremental drive bending Angle of BSPU1 is about 14°@12.78 V/μm,which is almost 1.6 times that of BSPU4 at the same electric field intensity.(3)Using two-color printing ink fine direct writing 3D printing equipment(DIW),the BNPU/BSPU double-layer elastomer products with gridded hollow structure of BSPU and BNPU layer alternately stacked(LBL)were prepared.The dielectric properties of BNPU/BSPU bilayer elastomers are enhanced greatly due to their strong donor-acceptor(D-A)polarization at the interface.Compared with the DEA structure prepared by BNPU and BSPU slurry,the dielectric constant of BNPU/BSPU double-layer printing structure is about 17.64@10~3 Hz,which is about 2.6 times of the Angle increase of the other two groups of samples under the same electric field intensity.By designing the molecular chain side base and crosslinking structure,enhance the capacity of the polymer interface polarization,balance the electrical and mechanical properties of the polyurethane based dielectric elastomers;At the same time,a macroscopic three-dimensional structure design was carried out to reduce the overall modulus of the material and construct the dielectric elastomer structure with(D-A)effect.This work provides theoretical basis and practical basis for the design and preparation of polyurethane based dielectric elastomer actuators with balanced electro-mechanical properties and applied in the field of flexible robots.