Preparation And Properties Of Hemicellulose-Based Functional Conductive Hydrogels

As a natural polysaccharide polymer,hemicellulose has the characteristics of renewability,hydrophilicity and biocompatibility.It can be used for the synthesis of functional hydrogels in the fields of biomedicine and tissue engineering.Among them,conductive hemicellulose-based hydrogel has great potential in stimulating cell activity and preparing flexible sensors.In present research,hemicellulose was used as the natural hydrophilic raw material,and conductive polymers,polyvinyl alcohol,glycerin,and tannic acid were introduced to synthesize functional composite conductive hydrogels.The structure and functional properties were studied,specially the application in the field of flexible strain sensors,which will provide a reference for the functional development of hemicellulose.The major research includes the following aspects.Hemicellulose-based conductive hydrogel was prepared using hemicellulose as the backbone and carboxy-terminated conductive aniline pentamer?CTAP?by one-pot chemical crosslinking in Na OH solution.The hydrogel had a high thermal stability and uniform porous structure,and its pore size decreased as the increasing of the contents of CTAP.The hydrogel exhibited high swelling capacity,and maintained a stable network structure after swelling for 15 h.The conductivity of the hydrogel was 2.11×10^-3 S/m,which was adequate for the electrical activation of biological cells.The hemicellulose/polypyrrole was firstly synthesized by polymerization of pyrrole monomers using hemicellulose as a hydrophilic carrier.After physical crosslinking with hemicellulose/polypyrrole,glycerol,polyvinyl alcohol and borax,the multifunctional composite hydrogel was synthesized by soaking in Na Cl solution.As compared with polypyrrole,the contact angle of hemicellulose/polypyrrole reduced to 58.7°,which indicated the increase of the hydrophilicity.The introduction of glycerol and Na Cl reduced the freezing and thawing temperatures of the hydrogel to-43.1 and-22.1°C,respectively.With the multiple hydrogen bonds and borax complexation formed in the network,the tensile stress and strain of the hydrogel were 319.7KPa and 142.85%,respectively.The hydrogel exhibited reshaping ability,and had high water retention capacity contained after 7 days of storage.The hydrogel had a conductivity of 5.14 S/m,and its relative resistance change reached 2456.7%at a strain of 500%.The wearable strain sensor assembled by hydrogel accurately and stably monitored the bending signals of finger,wrist flexion,and throat deformation during drinking and talking,which has promising applications in sports and health monitoring.A transparent hemicellulose-based multifunctional hydrogel was prepared by incorporating hemicellulose/polypyrrole,polyvinyl alcohol,and tannic acid into the polyacrylamide network.The free radicals generated by ammonium persulfate continuously reduced the agglomerated particles of polypyrrole and allowed visible light to pass through the network.The hydrogel maintained a light transmittance of 79.6%at a thickness of 2 mm,and its conductivity reached 3.12 S/m.The tensile stress and strain of the hydrogel were 319.7 KPa and 142.85%,respectively.It could adhere stably and reproducibly to various materials including skin.Due to good relative resistance change and gauge factor under strain,the wearable strain sensor assembled by the hydrogel prepared monitored quickly and accurately the strain sensing signal of the forefinger and elbow bending as well as pulse beating after rest and exercise,which has promising applications in sports monitoring and personal medical diagnosis.