Synthesis, Structure And Performance Characterization Of Novel Cellulose-based Conductive Hydrogel

In recent years，with the shortage of oil and gas resources and the increasing demand forenvironmentally friendly and biocompatible functional products，new functional materialsbased on cellulose is gradually becoming a hot research topic. Cellulose-based hydrogels havearosed great interests of domestic and foreign researchers owing to their potential applicationsin the fields of biomedical, controlled drug release and tissue engineering materials. Previousresearches on cellulose-based hydrogels mainly focused on the pH-sensitive andtemperature-sensitive hydrogels, there are few studies on preparation of conductive hydrogelsfrom cellulose resources. Morever, conductive polymer hydrogel is widely studied since it cancombine the unique swelling property of hydrogels with the excellent electrical and opticalproperties of conductive electroactive polymers.In this thesis, a novel cellulose-based conductive hydrogel was prepared via conventionalinterpenetrating polymer network method using microcrystalline cellulose as raw material andpyrrole as the monomer of conductive polymer. The electrical conductivity, thermal stability,mechanical and swelling properties as well as the molecular microstructure werecharacterized by thermo-gravimetric analysis, scanning electron microscope, four-probeelectrical conductivity and mechanical property testing and other testing methods. The factorsthat affected the propeties of the composite hydrogel were also investigated by analyticalmethods such as FTIR, XRD, XPS and so on.It is found that the obtained conductive hydrogels had a uniform and stablesemi-interpenetrating network structure whose conducitivity could be reach10-3to10-4S cm-1,and the conductivity was expected to be further increased to the order of magnitude of10-2byintroducing various dopants. Among the four selected dopants, hydrogels doped by BSNashowed the highest conductivity which was up to1.1×10-2S cm-1; the electrical conductivityof the composite hydrogel increased and then decreased with the increasing of theconcentration of dopant; the composite hydrogel with various cellulose content showedsimilar swelling kinetics and the equilibrium swelling ratio (ESR) was up to500%; with theincreasing of the concentration of oxidant, the conductivity and mechanical properties of composite hydrogels displayed a downward trend after the first rise, and both of themachieved the maximum values when the oxidant concentration was0.3M, which were9.18×10-3S cm-1and26.25Mpa, respectively; the increase of the crosslinking agent rendered theincreased crosslinking density and shrinkage stress of the hydrogel network accordingly,resulting in a decline in the ESR of the hydrogel, while the mechanical strength was increasedfirstly and then decreased. SEM, FTIR and XPS results proved that the differences in therelevant properties of hydrogels were rooted in the corresponding change of their chemicalcomposition and microstructure.This thesis showed that it is entirely feasible to prepare conductive hydrogel with goodswelling, electrical and mechanical properties along with thermal stability by strictlycontrolling the synthetic conditions. The obtained cellulose-based conductive hydrogel ispromising to be applied in the fields of biomedical, sensors and dye separation, etc.