Preparation And Properties Of Conductive Composite Hydrogels

Conductive hydrogels (CHs) are polymeric blends or co-networks that combine inherently conductive electroactive polymers (CEPs) with highly hydrated hydrogels, and can be the candidate for capacitor, sensor and actuator. Through copolymerization, crosslinking or grafting into integrate, both of the constituents play a role in tuning the final hybrid material’s properties. Meanwhile, the methods and conditions of synthesis can greatly influence the final material properties such as microstructure and gross morphology on account of subtle contributions of various factors. So it’s necessary to consider each aspect for conducting the synthesis. Herein, on the basis of survey and summary to the previous literatures on the preparation and correlation properties of conductive hydrogels, the combination of γ-irradiation crosslinking polymerization and grafting polymerization is a highly efficient method to prepare a conductive polyaniline composite hydrogel in this work. And, taking advantage of piercing effect of PEO through cyclodextrin, a graphenc oxide supramolecular conductive hydrogel is designated. The details as described below:1. Polyacrylamide-g-polyaniline composite hydrogels possessing both good mechanical strength and excellent conductivity were prepared through two-step polymerization method. First of all, N-(4-aminophenyl)acrylamide (APAm) was synthesized to provid pendant groups for grafting polyaniline, and underwent copolymerization with acrylamide under γ-irradiation, which also induced the crosslinkage of polymer chains. Thus, P(Am-co-APAm) hydrogels were produced. The storage modulus and fracture stress of those hydorgels could reach up to the magnitude of 104 Pa, the fracture strain to 550%. The second step is grafting polymerization between aniline absorbed in the pores of hydrogel in advance and the aminophenyl side groups of the hydrogel matrix with ammonium persulfate as oxygenant. After acid doping, the final conductive hydrogels of P(Am-co-APAm)-g-PANI were obtained. In the experiment, changing irradiation duration and irradiation dose rate was done to explore the influence of total dose on the copolymerization and crosslinkage. The results show that with the increment of irradiation dose, the swelling degree of P(Am-co-APAm) hydrogel increases at first but decreases later, while gel fraction increases continuously. This suggests that the crosslinking degree of P(Am-co-APAm) hydrogel changes with irradiation dose. In addition, the monomer concentration also affects the mechanical properties and swelling property of P(Am-co-APAm) hydrogels. Importantly, the resulted P(Am-co-APAm)-g-PANI composite hydrogels have relatively continuous PANI phase, leading to excellent conductivity as high as 9.3 S/m. Therefore, the excellent composite hydrogels in this thesis has great potential application in electrochemical switching devices.2. Taking advantage of the inclusion complex formed with β-cyclodextrin and poly(ethylene glycol), the formation of graphene oxide conductive supramolecular hydrogel from graphene oxide modified with β-cyclodextrin and Pluronic F127 is desiganted. On the one hand, graphite oxide (GO) was prepared from the natural graphite powder (700 mesh) according to the modified Hummers’ method, then through the esterification of propargyl alcohol with carboxylic group of GO surface, the alkynyl group was indroduced onto GO successfully. On the other hand, using p-toluenesulfonyl chloride (TsCl) and sodium azide (NaN3),β-cyclodextrin with azido group is obtained. Then conducting the click reaction of GO containing alkynyl group and β-cyclodextrin containing azido group resulted in the attachment of β-cyclodextrin on the surface of GO. Thus, once the aqueous dispersion of GO modified with β-cyclodextrin was mixed with the solution of Pluronic F127, a graphene oxide supramolecular hydrogel will be formed.