Preparation And Properties Of Multifunctional Conductive Composite Hydrogels

Hydrogels is a kind of hydrophilic polymer with water as dispersing medium and network cross-linked structure.Due to its good biocompatibility,non-toxicity,swelling and good flexibility,it has been widely used in various fields,such as drug delivery,energy storage devices,biosensors,wearable devices and tissue engineering scaffolds.However,due to the poor mechanical strength and electrical conductivity,the more expanded applications are limited.Therefore,preparation of multifunctional hydrogels with two or more important functions such as electrical conductivity,self-healing properties,toughness and ductility,has become a hot topic in this field.The applications as electronic skin or ionic skin to detect the human health condition and motion sensors,as well as medical materials such as helping wound healing and skin repairring have also attracted many attentions in recent years.Based on a brief review of multifunctional hydrogels,the following works have been completed in this thesis:1.Using the one-pot method,a highly free-shapeable and stretchable conductive self-healing nanocomposite hydrogel was prepared by embedding Ag nanoparticles and reduced graphene oxide（RGO）nanocomposites（Ag/RGO）,and its chemical structure,morphology,mechanical properties,self-healing properties and electrical conductivity were characterized.The results show that the hydrogel has high electrical conductivity(4.43 S·m^-1)and good flexibility.The self-healing efficiency can achieve 97.6%within 30 seconds without any external stimuli.It also exhibits an excellent free-shapeable property like clay such that it can be modeled into any different complex geometrical shape as desired.Therefore,it has potential applications in many fields,such as flexible electronic wearable devices,sensors,rechargeable batteries and biomaterials.2.Polypyrrole（PPy）particles were prepared by glow discharge electrolytic plasma initiation and doped into a hydrogel system to prepare a multifunctional cellulose-based conductive hydrogel with aluminum ion(Al³⁺)cross-linked polyacrylic acid（PAA）,and the mechanical properties,self-healing properties and electrical conductivity of hydrogels were determined.The results show that the hydrogel exhibited high electrical conductivity(2.79 S·m^-1),excellent mechanical properties（tensile strength of 0.309 MPa,fracture strain of 750%）,and good self-healing performance.The self-healing efficiency reached 91.9%within 9 h at room temperature without external stimulation.The results provide a inspiration for the development of biosensors with excellent mechanical properties and wearable flexible devices with self-healing properties.3.The self-healing hydrogel with excellent electrical conductivity and mechanical properties was obtained by doping PPy particles into iron ion(Fe³⁺)crosslinked PAA and chitosan（CS）polymer hydrogels,and the chemical structure,morphology,mechanical properties,self-healing properties and electrical conductivity of the prepared hydrogels were characterized.The results show that the conductivity of the hydrogel can reach 2.61 S·m^-1,tensile strength of 0.33 MPa,fracture strain of 628%and an elastic modulus of 0.146 MJ·m^-3,toughness of 1.14MPa.Further,its self-healing efficiency is as high as 93%after 9 h of healing in the air without any external stimulus.Therefore,with these outstanding mechanical,self-healing,and conductive abilities all in one,it is possible to fabricate a new kind of soft material with wide applications.