Study On Performance Improvement And Functionalization Of Conducting Polymer/cellulose Fiber Composites

Currently,the development and application of cellulose fiber has been the focus of research because cellulose fiber is one of the greatest treasures of nature.Especially for the research of its functionalization,the obtained cellulose fiber has a wide application field based on the excellent properties of cellulose fiber and the special functions of the materials adopted for modification.The researches that make cellulose fiber obtain many kinds of functions belonged to conducting polymers through in situ polymerization have been paid close attention by plenty of researchers.However,the strength of the material become poor because hydroxyls of cellulose are covered by conducting polymers deposited.The dedope of conducting polymer due to larger specific surface area of cellulose fibers and frequent contact with air or water solution in the storage process limits the application of conducting polymer/cellulose fiber composite.In this study,the methods of in situ polymerization of conducting polymers in aqueous cellulose fibers were used and multifunctional conducting polymer/cellulose fiber composites which had the properties of conducting,flame retardant and bacteriostasis were prepared.The strength of the composites was improved by selecting the doping agent containing various functional groups which could provide additional hydrogen bonds between polymer molecules.Moreover,self-doped conducting polymer/cellulose fiber composites were obtained by changing the traditional doping method which solved the dedoping problem of conducting polymer.The study provides a theoretical and technical basis for the wide application of conducting polymer/cellulose fiber composites.In the study,p-toluenesulfonic acid(PTSA)and sulfosalicylic acid(SSA)were utilized as dopants to prepare bifunctional polyaniline/cellulose fiber composites.The results showed that the electrical conductivity and flame retardancy of the composites were greatly affected by the type and the concentration of doped acid.Electrical conductivity,conductivity stability and strength properties of SSA doped samples were better than those of PTSA doped ones and previously studied inorganic acid doped ones.The excellent performances of SSA doped samples were derived from their better doping level and more intermolecular hydrogen bonds supplied by SSA addational acidic groups which had been confirmed by XPS and SEM characterization.Self-doped polyaniline/cellulose fiber(SPANI/CF)composites could be obtained with cellulose fiber as carrier and aniline(ANI)and m-aminobenzenesulfonic acid(MAA)as raw material by means of in situ copolymerization,which owned better ability of dedoping resistance in ammonia solution.The optimum conditions of SPANI/CF preparation were obtained by single factor experiment,i.e.,under the condition of ice bath,the total mole amount of reactants is 0.07 mol,the optimum molar ratio of MAA:ANI is 2:1,the molar ratio of reactants to ammonium persulfate is 2:1,hydrochloric acid concentration is 1.2 mol/L,and the reaction time is 105 min.Self-doping could not improve the electrical conductivity of the composite,but it could improve the flame retardancy.After soaking treatment of ammonia solution,both the conductivity and the oxygen index of self-doped polyanilin/cellulose fiber composite decreased.ATR-FTIR,XPS and SEM were used to show deprotonating process after ammonia treatment.Subsequently,its excellent dedoping resistance was due to the fact that sulfonic groups located in the SPANI benzene ring were durable against ammonia treatment.PPy/cellulose fiber composites(PPy/CF)with excellent strength properties could be prepared by selecting the oxalic acid(OA),citric acid(CA)and sulfosalicylic acid(SSA)as the dopant in the pyrrole polymerization process.Meanwhile,the acid concentration significantly affected the performance of PPy/CF composite.The results showed that additional hydrogen bonding between the polypyrrole molecules supplied by dopant could provide better strength properties.For the three doped acids,SSA doping had the highest doping efficiency which engenders the best comprehensive performance of SSA-PPy/CF.When SSA concentration was 0.02 mol/L,the conductivity and the tensile index could reach 18.25 S/m and 19.32 Nm/g,respectively.Sodium lignosulfonate(SLS),as the dopant,could enhance the strength properties of polypyrrole/cellulose fiber(PPy/CF)obtained by in-situ polymerization.The results showed that the strength performance of SLS-PPy/CF could be greatly improved by additional hydrogen bonds formed between polypyrrole molecules and polypyrrole particles compared with FeCl3(FC)and PTSA doped.When the dosage of SLS was 0.5 g,the tensile index of SLS doped PPy/CF was about 20 Nm/g which is restored to half of the strength of the original cellulose fibers.However,its conductivity decreased slightly.The molecular weight and dosage of SLS had different effects on the conductivity and the strength of PPy/CF.Besides,in a certain dosage range,the high molecular weight SLS could provide stronger strength performance,but its conductivity is poor.With the increase of SLS dosage,the conductivity of SLS-PPy/CF declined.Phytic acid is a kind of organic phosphine compounds extracted from plant seeds and is abundant in nature.In this study,the conducting polymers(PPy,PANI)/cellulose fiber composites with conductive,flame retardant and antibacterial properties were prepared.The conducting polymers(PPy,PANI)/cellulose fiber composites with conductive,flame retardant and antibacterial properties could be obtained by utilizing phytic acid chelation with metal ions and metal ion antibacterial effect by the in situ polymerization method.The results showed that,although the conductivity of the zinc phytate doped conducting polymer/cellulose fiber composites decreased compared with the zinc sulfosalicylate doped due to the low doping level of phytic acid,it could provide good antibacterial properties(especially for Staphylococcus aureus)and flame retardant properties for conducting polymer/cellulose fiber composites because of the introduction of more flame retardant components into the polymer chain.Futhermore,phytic acid concentration had a great effect on the properties of the composites.The study also showed that PPy/CF and PANI/CF could achieve the best property while phytic acid concentration was 0.2 mol/L and 0.3 mol/L,respectively,which was due to the different polymerized mechanisms of PANI and PPy.