Preparation And Properties Of Natural Polysaccharide-based Multi-functional Conductive Hydrogels

Conductive hydrogel,a crosslinked and water-containing polymer network equipped with intrinsic flexibility and conductivity,has shown enormous potential of practical application for biosensors,E-skin and so forth.So far,most conductive hydrogels still cannot meet various practical requirements,due to the plain mechanical properties,bad biocompatibility and mono-functionality.Herein,combined with nanocomposite（NC）and polymer network regulation technology,three polysacchride-based multi-functional conductive hydrogels have been developed in this study.1)A novel type of hydrogels was prepared via two-step in-situ radical polymerization of acrylamide（AAm）and aniline（Ani）monomers in the matrix of graphene oxide（GO）and chitosan（CS）via Li OH/urea solvent.The synergetic integration of NC and multinetwork（multi-N）endowed PAni/PAAm/GOCS hydrogels with excellent mechanical properties.Besides,the morphology and structure of PAni nanofiber networks were subtly adjusted by changing the proportion of phytic acid/HCl,resulting in the increment of conductivity and mechanical properties.Eventually,the tensile strength,elongation and conductivity could reach 0.8 MPa,360%and 2.88±0.07 S/m,respectively.Furthermore,the remarkable strain-sensitivity and skin affinity of PAni/PAAm/GOCS hydrogels were characterized utilizing four-point probe and allergy patch tests.The strategy to design tough,stretchable and conductive hydrogels by NC and multi-N provided such hydrogels great possibility of practical application for strain sensors.2)Through the one-pot in-situ radical copolymerization of 2-（methacryloyloxy）ethyl]dimethyl-（3-sulfopropyl）ammonium hydroxide（SBMA）and AAm in alginate aqueous solution,a multi-functional Alginate/P（SBMA-co-AAm）conductive hydrogel was successfully fabricated.The-N⁺（CH₃）₃ and-SO₃^-on SBMA could separate easily during the process of ion migration,endowing the hydrogel with high ionic conductivity.In the meantime,this hydrogel exhibited excellent adhesiveness to various substrates via ion-dipole or dipole-dipole interaction of zwitterionic molecules.The copolymerization with AAm brought outstanding flexibility and stretchability.Alginate,as a part of semi-interpenetrating polymer networks,made the hydrogel stronger and biocompatible.Finally,the tensile strength,elongation,compression strength,conductivity and adhesion strength were 133.8 k Pa,1353%,122.5 k Pa,0.15 S/m and 6.04 k Pa,respectively.What’s more notable was that the biocompatibility and self-cleaning function tested by MTT,Live/dead assay,allergy patch tests and plate colony-counting method imparted great possibility of practical application for strain sensors to hydrogels from a biological point of view.3)Inspired by the mussel-chemistry,GO was used to imitate the structure of mussel cupule.The limited nanospace between GO layers could mediate the self-polymerization of dopamine hydrochloride（DA）and prevent the over-oxidation of PDA.GO@DA nanofillers with abundant catechol groups were prepared.Mixed GO@DA dispersion with alginate,acrylic acid（AAc）and AAm,the GO@DA/P（AAc-co-AAm）/Alginate multi-functional hydrogel was obtained via one-pot radical copolymerization method.GO@DA not only acted as the nanofiller,but also implanted the hydrogel remarkable adhesiveness and electrical conductivity.The hydrogel matrix had a double-network structure using Fe³⁺and N,N’-methylenebisacrylamide as physical and chemical crosslinkers,respectively.After adjusting the content of DA and alginate,the integration of tensile strength（320.2 k Pa）,ultrastretchability（1198%）,adhesiveness（36.9 k Pa）,conductivity（3.24±0.12 S/m）,strain-sensitivity（y=0.00703 x²+1.53766 x-2.8862）,self-healing ability and biocompatibility provided the hydrogel with tremendous possibility of practical application for strain-sensors.