Study On Sulfonated Poly(Phthalazinone Ether Ketone Ketone)s As Proton Exchange Membranes

In this thesis,several kinds of sulfonated poly(phthalazinone ether ketone ketone)s (SPPEKKs)have been synthesized based on the molecular design principle under the background of the application of sulfonated poly(arylene ether keton)s in proton exchange membrane fuel cells(PEMFC).Correlative performances of all polymers are studied in order to find a novel membrane material with good properties in PEMFC application.Two sulfonated monomers 1,4-bis(3-sodium sulfonate-4-chlorobenzoyl)bezene(SBCBB) and 1,4-bis(3-sodium sulfonate-4-fluorobenzoyl)bezene(SBFBB)are successfully prepared by sulfonation of 1,4-bis(4-chlorobenzoyl)benzene(BCBB)and 1,4-bis(4-fluorobenzoyl) benzene(BFBB)respectively with fuming sulfuric acid via aromatic electrophilic substitution reaction.FT-IR and ¹H-NMR are used to characterize the structures of sulfonated monomers'.Novel sulfonated poly(phthalazinone ether ketone ketone)(SPPEKK)with different sulfonation degree(SD)are synthesized via direct nucleophilic polycondensation from SBCBB(SBFBB),BFBB(BCBB)and 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ); sulfonated poly(phthalazinone ether ketone ketone)(SPPEKK-D)containing dimethyl groups with different sulfonation degree and high molecular weight are prepared by direct aromatic nucleophilic polycondensation of SBFBB,BFBB and 4-(3,5-dimethyl-4-hydroxyphenyl)-2,3-phthalazin-1-one(DMDHPZ);sulfonated poly(phthalazinone ether nitrile ketone ketone) (SPPENKK)containing dimethyl groups with different sulfonation degree and high molecular weight are obtained by direct nucleophilic polycondensation of SBFBB,2,6-difluoro benzonitrile(DFBN)and DMDHPZ.Polymers' structures are characterized by FT-IR and ¹H-NMR.All polymers have good solubility in polar aprotic solvent such as NMP,DMAC and DMSO.Sulfonated poly(phthalazinone ether ketone ketone)s films are prepared by solution casting method.Membranes' properties such as water uptake,swelling ratio,oxidative resistance,ion exchange capacity(IEC)and proton conductivities have been measured.Water uptake,swelling ratio,IEC and proton conductivity increased with the increasing SD. However,oxidative resistance decreased with SD increasing.The tensile test results show that tensile stress is above 46Mpa and Young's Modulus is above 1.5Gpa,which indicates sulfonated poly(phthalazinone ether ketone ketone)s films have good mechanical stability. Polymers with different structures have different performances,and performance details are given to make some comparison.The 5%weight loss temperature of these polymers is above 448℃(in sodium form)and above 331℃(in acid form),respectively,indicating they have good thermal stabilities.The SPPEKK-D membranes have the best oxidative stability, probably due to the introduction of dimethyl groups which substitute the active hydrogen atoms at the ortho position of phenolate oxygen atom.Transmission electron microscope (TEM)is used to study the membrane's micro-morphology.Compared with other polymers, SPPENKK membrane with a same SD has a much higher water uptake,IEC value and proton conductivities;the ionic-clusters' density in them is much higher and their average size becomes larger.Moreover,the hydrophilic phase becomes more continuous and the phase-separation becomes more obvious.This might because of the introduction of polar and hydrophilic cyano groups into SPPENKK's main chain.When temperature is above 80℃,all polymers with SD more than 0.8 show good proton conductivities(＞10^-2S·cm^-1),which meets the requirement in PEMFC application.