Studies On Preparation And Properties Of Cellulose Based Electroactive Materials

Smart materials with versatile and intelligent play an important role in military,architectural and daily life fields.The electroactive material,as a kind of intelligent material,can produce deformation and deflection displacement under the electric field,or generate response charge under stress.Them have broad application prospects in the fields of actuators,sensors and flexible bionic robots.The cellulose-based electroactive material is composed of the cellulose substrate and surface electrodes.the material will produce a certain degree of bending or deformation when a certain voltage was applied to the electrodes.The reason for its deformation mainly include two aspects,one is the deformation caused by the piezoelectric effect of the cellulose fiber,and the other is volume expansion caused by the diffusion and movement from the residual ion and water molecules inside the cellulose matrix under the electric field.Cellulose materials have the advantages of light weight,high strength,renewable,biodegradable,etc.,but the drive output and drive frequency of cellulose-based electroactive materials are low.At the same time,due to the cellulose substrate with poor water retention performance,humidity changes of environmental will greatly affect its actuation performance.In this thesis,cotton fiber(CPF)and chitosan(CTS)as raw materials are dissolved in the ionic liquid 1-ethyl-3-methylimidazole acetate([EMIM] Ac)form a chitosan/cellulose composite film material with an interpenetrating network structure by spin coating.It was immersed in 8% [EMIM] Ac solution.then a conductive polymer poly(3,4-ethylenedioxythiophene):poly styrene sulfonate(PEDOT:PSS)was deposited on the surface as electrode to obtain cellulose-based electroactive composite material.Scanning electron microscopy(SEM)showed that the surface of the composite film material(WCPF:WCTS = 9:1)was denser and the internal structure was more uniform.Compared with the pure cellulose membrane,the water absorption rate of the composite film was reduced by 46.8%,and the water retention rate was increased by 34.6%,which showing better resistance to environmental humidity changes.At the same time,the mechanical properties of the composite film were also greatly improved over the pure cellulose film,the tensile strength was increased by 53.7%,and the Young's modulus was increased by 72.5%.X-ray diffraction and thermogravimetric analysis showed that the crystallinity of the composite film material was improved after doping with ionic liquid [EMIM] Ac,but the thermal stability was slightly reduced.The maximum electroactive displacement of chitosan/cellulose electroactive materials doped with ionic liquids at 10 V DC voltage can reach 7.3 mm,which was 2.3 times higher than pure cotton fiber materials under the same conditions.Secondly,the paper selects two kinds wood pulp dissolving pulp with the content of ?-cellulose exceeding 93% and the relative crystallinity exceeding 82% as the raw material dissolved in the [EMIM] Ac to obtain the regenerated cellulose film.Then a gold electrode was deposited on the surface of the film using ion sputtering method to obtain a wood fibers cellulose-based electroactive material.Fiber analysis results showed that the main difference between the two types of wood pulp was ash content and iron and copper ion content.The ash content of wood pulp fiber(WPFC)was 0.12%,and the total iron and copper ion content was 4.45 ppm.The ash content of wood pulp fiber(WPFH)is 0.06%,and the total content of iron and copper ions was 5.64%.Comparing the two methods of forming the surface electrode of the composite material,that is,ion sputtering method deposited gold electrode(Au E)and the film surface deposited PEDOT:PSS to form a conductive polymer electrode(CPE).The electroactive performance of the former was significantly higher than the latter.The electroactive displacement of the cotton cellulose film with the gold electrode and the chitosan/cotton cellulose composite film were higher than that of the conductive polymer electrode.the maximum deflection displacement of the Au E(CPF-IL)film reached 10.5 mm,while the Au E(CPF/CTS-IL)film reached 15 mm.The electroactive performance of the electroactive materials prepared by two kinds wood pulp fibers showed a great difference.The maximum deflection displacement of Au E(WPFC-IL)film was 5.1 mm,while Au E(WPFH-IL)film was 23 mm.Finally,the thesis using TEMPO oxidized nanocellulose fiber(TOCNF)with high-crystallinity as the raw material,self-assembles prepared film by solvent evaporation.and then depositing gold electrode on the surface by ion sputtering to obtain nanocellulose-based electroactive composite materials.Scanning electron microscope results showed that the TEMPO oxidized nanocellulose fiber film has a uniform and dense structure.With the increase of the thickness of the TOCNF film,the thermal stability of the film has not changed,but the mechanical properties have been greatly improved.When the film thickness reaches 14 ?m,its tensile strength exceeds 107 MPa,and the Young's modulus reaches 14.9 GPa.The film with thickness of 4.7 ?m has a tensile strength of only 23 MPa and a Young's modulus of 4.71 GPa.The thickness of the TOCNF film has an important impact on the maximum deflection displacement and response time of the material.Too thick or too thin is not conducive to the improvement of the electroactive performance of material.The response performance of the material continues to improve when the applied voltage of the material increased from 3 V to 10 V.The TOCNF composite film material with a thickness of 10.8 ?m Au E(TOCNF-d)exhibited extremely excellent electroactive performance applying a 10 V DC voltage.It deflected rapidly and had the maximum tip displacement exceeds 32 mm within a few seconds.The material can be quickly folded back when changing the voltage direction,at this time the maximum reverse deflection displacement reaches 42.5 mm.