Preparation And Characterization Of Chitosan-based Double Network Hydrogel

The gel is difined as the special dispersion system that colloidal particles or macromolecules are interconnected to form the spatial network structure under the certain condition,whose voids are filled with the liquid as dispersion medium.Hydrogel is the gel with water as dispersant.It is a soft and wet material with some unique properties such as swelling/deswelling properties,responsiveness,repairability and electroconductivity,etc.Therefore,there are many potential applications in biological medicine,sensors and wound dressing,etc.However,their applications were limited by the poor mechanical properties.Due to the defect of the hydrogel,the purpose of this paper is to prepare functionalized double network hydrogels using chitosan（CS）.The details are as follows:（1）Chitosan（CS）was dissolved by aluminum chloride hexahydrate（AlCl₃·6H₂O）as the novel solvent instead of the traditional acetic acid（Ac）.High-strength and high-toughness double network hydrogel(CS/PAMAA-Al³⁺DN hydrogels)was synthesized with CS as the first network and the chemical covalent crosslinked network through acrylamide（AM）and acrylic acid（AA）as the second network（PAMAA network）.The CS/PAMAA-Al³⁺DN hydrogels possess hydrid physical and chemical crosslinked network with ionic interaction between Al³⁺ions and CS and PAMAA chains.The results exhibit that the addition of AlCl₃·6H₂O could significantly improve the mechanical properties of the hydrogel and the CS/PAMAA-0.25 DN hydrogel prepared with the content of 0.25 g is equipped with the optimal mechanical properties,and its elongation and tensile strength is up to2203.7%and 0.54 MPa,respectively.Otherwise,the hydrogel also possess good self-recovery performance,and could recover above 96%of their original height at 80%compression strain for 10 cycles.（2）Based on the above CS/PAMAA-Al³⁺DN hydrogels,the thermo-responsive chitosan-based DN hydrogels（CNA DN hydrogels）were prepared with the introducting of N-isopropyl acrylamide（NIPAM）.The rheological properties,mechanical properties,transmittance and swelling behavior were studied.The data shows that the transmittance is up to 98.63%and 0.29%at 20 and 60℃,respectively.And the equilibrium swelling ratio of a series of CNA DN hydrogels varies with temperature,which demonstrates that CNA DN hydrogels possess thermosensitivity.What’s more,the lower critical solution temperature（LCST）were determined by differential scanning calorimetry（DSC）,and the LCST of the CNA-7.5 DN hydrogel is 36.6℃which is quietly close to body temperature.（3）Based on the above CS/PAMAA-Al³⁺DN hydrogels,a series of conductive chitosan-based DN hydrogels（CAA DN hydrogels）were prepared with addition of2-acrylamide-2-methylpropanesulfonic acid（AMPS）.And the CAA DN hydrogels were easily disposed,dipped into saturated sodium chloride（Na Cl）solution.The characterization of mechanical behavior and AC impedance demonstrate that tensile strength and conductivity are vastly raised,up to 0.41 MPa and 13.16 S·m^-1,respectively.Afterwards,electrochemical capacitors were sandwiched with self-mide carbon electroeds and the hydrogel as polyelectrolyte,and their capacitance properties were studied.The results show that the specific capacitance and stability of electrochemical capacitors are significantly improved.