Research On Ionized Bacterial Cellulose/polyaniline Composite Gel Electrolyte Membrane

With the surge of interest in miniaturized implanted medical devices,implantable batteries with small dimensions and biocompatibility are highly demanded.Generally,implantable cell is comprised of four components such as anode,cathode,separator membrane and liquid electrolyte.However,the usage of independent liquid electrolyte gives rise to some serious problems including leakage,flame and blast.Subsequently,the replaceable electrolytes such as gel polymer electrolytes(GPEs)were created.Although GPEs possess satisfactory performances,some problems still remain unsolved,such as the high contact resistance between the electrolyte and electrode materials,and large fiber diameter of porous gel electrolyte,which limit the ion migration.Furthermore,few studies have been focused on the application of GPEs in biomedical field,so it is necessary to develop a kind of new gel electrolyte with good biocompatibility.In order to solve the problems with gel polymer electrolyte,we used bacterial cellulose,which has excellent three-dimensional network structure and abundant functional groups,as the matrix material.First,in-situ polymerization method was adopted to prepare bacterial cellulose/polyaniline(BC/PANI)composite gel membrane.The performance of BC/PANI prepared under different conditions was examined,and the optimum reaction condition was determined.Secondly,to improve the ionic conductivity of the electrolyte membrane,we chose three groups with different ionization intensity(carboxymethyl,carboxylate radical,sulfonate)to modify BC.BC was grafted with carboxymethyl,carboxylate radical and sulfonate,and then composited with PANI to obtain modified BC/PANI composite gel membrane.The influences of different groups to the microstructure,electrochemical property,mechanical property,thermal stability and biocompatibility were compared,and the mechanism of ion transportation were analyzed.The research findings are as follows:(1)In-situ polymerization method was adopted to prepare the BC/PANI composite gel membrane.The influences of the reaction conditions such as doping acid concentration,reaction time and water content to the properties of the composite gel membrane,especially the conductivity.were analyzed.The optimal reaction condition was obtained.The composite gel membrane was characterized by FT-IR.SEM,mechanical test and TG analysis.We found that.the addition of PANI improves the proton conductivity,and that low water content could improve the composite content of PANI and improve the electronic conductivity.However,excessive PANI content would reduce the various performances of the composite gel membrane,such as the electrical and mechanical properties.(2)Carboxymethyl and carboxylate radicals were introduced into the nanofibers by alkalization,etherification and oxidation.We used the in-situ oxidative polymerization method to prepare carboxymethylated bacterial cellulose/polyaniline(CM-BC/PANI)and carboxylated bacterial cellulose/polyaniline(CA-BC/PANI)composite gel membranes.The two composite gel membranes were characterized by FT-IR,SEM,four-probes tech,alternating current impedance,mechanical test and TG analysis.The experiment results showed that,the introduction of carboxylate radical not only improved the ionic conductivity(2.86x10-4 S/cm),but also retained the mechanical property of BC to some extent.By introducing the carboxylate radical via partly oxidation,it should improve the content of carboxylate radical in theory,and improve the ionic conductivity.However,with this method,it is hard to obtain composite membrane with a certain strength,and difficult to measure the conductivity.(3)A two-step reaction method was adopted to prepare sulfonated BC(SBC),and SBC/PANI was further obtained.The composite membrane were characterized by FT-IR,X-ray photoelectron spectroscopy(XPS),Energy Dispersive Spectrometer(EDS),SEM,mechanical test and alternating current impedance.FT-IR,XPS and EDS results showed that sulfonic acid groups were successfully grafted to the fibers of BC.SEM showed that sulfonation did not influence the morphology after incorporation of PANI.TG curves showed that sulfonation had little influence on the thermal stability of BC.The ionic conductivity of the SBC/PANI composite membrane was greatly improved;the best ionic conductivity was 5.25×10-3 S/cm.which was by 1?2 order of magnitudes larger.Linear volt-ampere scanning curve confirmed the electrochemical stability window the of the composite gel membrane was higher than 1.5V.Measurement of the ion-exchange capacity and the degree of sulfonation showed that,the ionic conductivity was related to the degree of sulfonation;Proton transportation were completed by the combination of the Grotthuss and vehicle mechanism.(4)CCK-8 experiments were carried out to examine the cytotoxicity of the BC/PANI,CM-BC/PANI,CA-BC/PANI and SBC/PANI composite gel membranes.It was found that none of these composite gel membranes showed obvious cytotoxicity,and the cytotoxicity were all below grade 1.The cells on the surface of the materials were dyed and observed under fluorescence microscope.It was found that all BC fibers were covered with PANI;whether it was modified or not,the BC membranes showed good cell attachment.SBC even promoted cell growth,and the cells on it showed better viability than those on pure BC.After incorporation of PANI,the number of dead cells on the surface of the material increased.Still,there were living cells attaching on the material.SBC/PANI showed the highest number of living cells.This revealed that sulfonation promoted cell proliferation.Cytotoxicity and cytocompatibility study of the BC-based gel electrolyte membranes provides experimental foundation to their application in the biomedical field.