Design And Preparation Of Proton Conductive Materials With High Local Sulfonation Degree

Proton conducting materials are synthesized via post-sulfonation modification of existing polymers or polymerization of sulfonated monomers with high local sulfonation degree or phosphonation degree.These materials possess suitable hydrophilic/hydrophobic balances,form hydrophilic/hydrophobic micro-and nano-phase separated morphologies under fully hydrated states,and faciliate long distance proton transport,and enhance proton conductivity.During the post-sulfonation modification of existing polymers,side-chain optimized poly(2,6-dimethyl-1,4-phenylene oxide)-g-poly(styrene sulfonic acid)(PPO-g-PSSA)is designed with balanced water-resistance and sulfonation degree by the combination of molecular dynamic simulation and experimental method.The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization(ATRP)from brominated poly(2,6-dimethyl-1,4-phenylene oxide)(PPO-x Br)and p-ethyl styrene sulfonate and followed by hydrolysis.The bromination degree(x)of PPO-x Br and polymerization degree(m)of the side-chains are varied to optimize the proton conductivity and the overall performances specifically to balance between the water-resistance and the sulfonation degree.It is concluded that proton conductivity with compromised water-resistance can be achieved at relatively low x(x<0.2)and high m(m>4).A maximum ion exchange capacity(IEC)of 3.24 mmol g^-1 is reached without the sacrifice of water-resistance.The optimized PPO-g-PPSA possesses a proton conductivity of 37.9 m S cm^-1 at 40°C and 90%relative humidity(RH),and45.5 m S cm^-1 at 95°C and 90%RH.During the polymerization of sulfonated monomers,a novel poly(ether ether ketone ketone)containing 1,4-butanedioxy spacer with pendent sulfopropyloxy side-chains is synthesized by Friedel-Crafts polyacylation under mild reaction condition.Firstly,1,4-diphenoxybutane(DPB)and diethyl 2,2'-(biphenyl-2,2'-diylbis(oxy))bis(propane sulfonate)(SBP-OEt)are synthesized as monomers.DPB introduces 1,4-butanedioxy aliphatic bridges into the polymeric backbone,and SBP-OEt dissolves in common solvents forming a homogeneous reaction mixture during the Friedel-Crafts polyacylation.The product exhibits the maximum proton conductivity of 152.5 m S cm^-1 at 95°C and 90%RH.In addition,the product exhibits an excellent dimensional stability,moderate water uptake of 53.2%at 100°C,and a relatively high IEC of 1.74 mmol g^-1.These characteristics are ascribed to micro-and nanophase separation enhanced by hydrophobic main-chains possessing flexible 1,4-butanedioxy spacer and hydrophilic sulfopropyloxy side-chains,such morphology facilitates the proton conducting and the water resistance.In comparison with morphology of high local sulfonated degree,morphology of high local phosphonated degree can also facilitate the hydrophilic/hydrophobic micro-and nanophase separation.Phosphonated polysulfone is synthesized by chloromethylation,hydroxylation,bromination,phosphorylation,and hydrolysis using polysulfone as polymeric backbone.The phosphonated side-chains are connected the the backbone via the rotatable ether bonds.The rotational freedom of phosphonated side-chains facilitate the segregation of hydrophilic clusters,enhance the hydrophilic/hydrophobic micro-and nanophase sepeartion,and strengthen the formation of proton transport channels and the proton conductivity.In addition,a synthetic route of phosphonic acid and trazolyl functionalized polysulfone is designed based on the synergetic effect proposed by our previous study.Phosphonated bromobenzene and PSF-CH₂-N₃ are synthesized by the azidation PSF-CH₂-Cl.