Preparation Of Conductive Cellulose Nanocrystals And Sensing Application Of Composite Materials

With the rapid development of wearable smart devices,the preparation of high-conductivity and controllable-performance composites has become crucial in the field of wearable technology.Furthermore,in order to comply with the theme of the green and environmentally friendly era and carbon reduction policies,the development of green and economical conductive nanocomposites is also a trend.The traditional preparation of conductive units and composite conductive networks has high economic costs,poor hydrophilicity,and poor mechanical properties and consumes a lot of energy,which greatly limits their widespread applications.Therefore,in this study,cellulose nanocrystals（CNC）with excellent properties such as high aspect ratio,good hydrophilicity,and biocompatibility were designed as biological templates.And CNC-3,4-polyethylene dioxythiophene（CNC-PEDOT）nanocomposites were prepared by hydrolysis of microcrystalline cellulose and in-situ polymerization of EDOT.A conductive hydrogel with a multiple network structure was then greenly constructed using this nanocomposite through a physical cross-linking method.The effect of different EDOT contents on the surface morphology and various properties of the CNC-PEDOT nanocomposite was investigated,and the sensing performance of the composites constructed by CNC-PEDOT was evaluated.which has huge application prospects in electronic skin,soft robots,and human-machine interaction fields.（Ⅰ）Preparation and properties of conductive cellulose nanocrystals.A one-pot green method synthesized a CNC-PEDOT nanocomposite with tunable morphology,and a series of characterization tests were carried out on it.SEM showed that the PEDOT nanoparticles in the CNC-PEDOT nanocomposite were firmly anchored on the CNC surface and had high electrical conductivity and good hydrophilicity and dispersion.With the increase of EDOT content,the conductivity and yield of its CNC-PEDOT nanocomposites are continuously improved,and the loading of PEDOT is also increasing.With the addition of 0.7 m L of EDOT monomer,the yield of CNC-PEDOT nanocomposites can reach 87.9%,and the PEDOT loading can reach 50%.Subsequently,wearable materials were successfully self-assembled by 0.15 wt%CNC-PEDOT_0.7 nanocomposite into the nonwoven fabric,and various sensing signals（human body activity changes and temperature changes）were monitored and exhibited good sensor responsiveness and stability.（Ⅱ）Regulation and properties of multiple network structures of CNC-PEDOT/polyvinyl alcohol composite conductive hydrogel.The CNC-PEDOT nanocomposites were introduced into polyvinyl alcohol/sodium alginate（PVA/SA）matrix material by freezing method and Ca²⁺crosslinking method,and CNC-PEDOT-polyvinyl alcohol/SA with multiple network structure was successfully constructed sodium alginate（CP-PVA/SA）conductive hydrogel.Through a series of characterization tests,the chemical structure,thermal stability,mechanical properties,high conductivity（490 m S/m）,high sensitivity（GF=68.7）,and various sensing responses of the CP-PVA/SA conductive hydrogel were investigated.The obtained CP-PVA/SA conductive hydrogel has a fast response and excellent stability to various deformations（stretching,bending,torsion,compression）,and a possible mechanism of compression sensing is proposed.In addition,the CP-PVA/SA conductive hydrogel to various activities of the human body has been found to have a corresponding regularity in the response of motion signals.Especially in monitoring gas（NH₃）,which also has excellent responsiveness and sensitivity.Due to its excellent sensing performance,it has great potential in applications such as wearable devices,electronic skin,and human-machine interaction.