Preparation And Property Of Sulfonated Poly (Arytehe Ether/Thioether) Proton Exhange Membranes With Phosphine Oxide Groups

Proton exchange membranes（PEMs）is the core material of pronton exchange membrane fule cells.Perfluorosulfonic acid ionomers（e.g.,Nafion）is the most widely used PEMs.However,there are disadvantages of low pronton conductivity at high temperature or low humidity,high methanol permeability,expensive production costs,which significantly limits its application.During the past years,sulfonated aromatic polymers are an important direction in the field of PEMs.Due to their outstanding comprehensive property,such as excellent thermal stability,high pronton conductivity and structure designability.Among them,sulfonated poly（arylene ether/thioether phosphine oxide）s which is developed by our group,are regarded as excellent materials for PEMs.Because the phosphine oxide moieties exhibit high oxidative stability,good water retention and excellent adhesive ability.However,like many other aromatic ionomer membranes,some of them showed excessive swelling,and their oxidative stability and mechanical property decreased,in the condition of high pronton conductivity.For the direct methanol fule cells（DMFCs）,besides the disadvantages of poor swelling resistance and oxidative stability,their methanol permeability still should be reduced to an acceptable extent.In this thesis,sulfonated poly（arylene ether/thioether phosphine oxide）s were prepared for DMFCs,which displayed high swelling swelling resistance and oxidative stability while maintaining considerable proton conductivity,by the introduction of strong intermolecular forces and the adjustment of microstructure.The main contents of the thesis are described as follow chapters:In chapter 2.Sulfonated poly（arylene thioether phosphine oxide）s（sPTPO）were prepared by polymerization of 1,4-benzenedithiol,bis（4-fluorophenyl）-3’-sulfnate phenyl phosphine oxide and bis（4-fluorophenyl）phenyl phosphine oxide at first.Sulfonated polybenzothiazoles（sPBT）show excellent oxidative stability and the least variation in their swelling during the whole temperature,due to the interactions between the sulfonic acid groups and benzothiazole moieties.To reduce the swelling,sPTPO were blended with sulfonated polybenzothiazoles（sPBT）to prepare composite proton exchange membranes（PEMs）because the sulfonic acid groups of sPTPO and the benzothiazole moieties of sPBT can form strong acid-base interactions.Herein,sPBT were for the first time employed as a blend component to fabricate blend PEMs.The resulting blend membranes exhibited remarkably enhanced overall properties.For example,one of them exhibited a swelling of only 16%and a proton conductivity of 0.085 S cm^-1 at 80°C（higher than that of Nafion 117）,and a methanol permeability of 1.02×10^-7 cm²/s.Moreover,it also displayed excellent thermal stability,oxidative stability and mechanical properties.In chapter 3.Trisulfonated poly（arylene ether phosphineoxide）s（tsPAEPO）were synthesized by polymerization of sulfonated bis（3-sulfonated-4-fluorophenyl）phenyl phosphine oxide,bis（4-fluorophenyl）phenyl phosphine oxide and phenylphenol,corresponding mono-sulfonatedpoly（arylene ether phosphineoxide）s（msPAEPO）were synthesized in the meanwhile.A comparative research indicated that the distribution patterns of trisulfonate polymers can promoted formation of novel phase separation microstructure,that tsPAEPO show larger but less connective ionic channels compared with the corresponding mono-sulfonated.Thus,tsPAEPO showed more excellent swelling resistance and oxides stability and lower methanol permeability.The result suggested that“trisulfonation approach”can be used for different kinds of dihydroxy monomer,and overall performance of the polymers could be enhanced by adjusting the structure of dihydroxy monomer.For example,tsPAEPO-150 showed a swelling of 14%,a conductivity of 0.11 S/cm,and a methanol permeability of 4.1×10^-7 cm²/s.Especially,the oxide stability is superior to other sulfonated aromatic polymers reported before.In chapter 4.Trisulfonated poly（arylene thioether phosphineoxide）s（tsPTPO）were synthesized by polymerization of sulfonated bis（3-sulfonated-4-fluorophenyl）phenyl phosphine oxide,bis（4-fluorophenyl）phenyl phosphine oxide and 4,4-thiobisbenzenethiol,corresponding mono-sulfonatedpoly（arylene thioether phosphineoxide）s（msPTPO）were synthesized in the meanwhile.Similar to the previous chapter,the distribution patterns of trisulfonate polymers can promoted formation of novel phase separation microstructure,and tsPTPO show larger but less connective ionic channels compared with the corresponding mono-sulfonated,which facilitated to excellent swelling resistance and oxides stability and lower methanol permeability.The result showed that“trisulfonation approach”have the same effect on the microstructure and properties for the trisulfonated poly（arylene thioether phosphineoxide）s.High performance PEMs was prepared after further optimization of reaction condition.For example,one of them showed a swelling of 21%and a conductivity of 0.087 S/cm at 80°C,and a methanol permeability of 0.98×10^-7 cm²/s.Moreover,it also displayed excellent thermal stability,oxidative stability and mechanical properties.In chapter 5.Polyvinylidene fluoride（PVDF）is hydrophobic polymer.The microstructure of trisulfonated poly（arylene ether phosphineoxide）s could be adjusted by blending with PVDF,and overall performance of membranes could be further improved.Due to the introduction of PVDF,blend membrane show more obvious phase separation and larger but less connective ionic channels,oxidative stability and selectivity was enhanced obviously.High performance blend membranes were prepared after further optimization of reaction condition.For example,it swelling and conductivity are 15%and 0.112 S/cm at 80°C,and a methanol permeability of 0.73×10^-7 cm²/s.The selectivity of blend membrane is thirty times larger than that of Nafion 117.Furthermore,it also displayed excellent thermal stability and oxidative stability.