Synthesis And Modification Of Sulfonated Poly(Phthalazinone Ether)s For Proton Exchange Membranes

Two kinds of sulfonated poly(phthalazinone ether)s with different degrees of sulfonation(DS) are synthesized via nucleophilic polycondensation in this thesis. 1,4-bi(3-sodiumsulfonate-4-fluorobenzoyl)benzene (SDFKK) is prepared by sulfonation of1,4-bi(4-fluorobenzoyl) benzene (DFKK) with fuming sulfuric acid containing 50% SO₃.Novel sulfonated poly(phthalazinone ether ketone ketone)s (SPPEKKs) are synthesizedwith different DS via direct polycondensation from SDFKK, DFKK and4-(4-hydroxyphenyl)-1(2H)-phthalazinone(DHPZ). The inherent viscosity of copolymers is inthe range of 0.43dL/g to 1.80 dL/g. Sulfonated poly(phthalazinone ether nitrile ketoneketone)s copolymers (SPPENKKs) are synthesized in high molecular weight via directpolycondensation from SDFKK, DFKK, 2,6-dicholobenzonitrile(DCBN) and DHPZ. Theinherent viscosity of copolymers is in the range of 0.62dL/g to 1.57dL/g.FT-IR, ¹H-NMR and wide-X-ray scattering are used to characterize the structures ofSPPEKKs and SPPENKKs. TGA is used to study the thermal properties of these copolymers.10% weight loss temperatures of the products are about 400 and 500℃, respectively. Twokinds of sulfonated polymers have excellent solubilities, and they can dissolve in polarsolvents. Tough films were obtained by solution casting method with N-methylpyrrolidone.The properties of these membranes have been studied in detail, which include solubility, wateruptake, swelling ratio, oxidative resistance, hydrolysis resistance, ion exchange capacity andproton conductivity etc. The results show that: the two kinds of copolymers perform verygood potential usages in DMFC.In order to overcome the shortcomings of the poly(phthalazinone ether)s membranes wehave taken SPPEKKs for the example and prepared SPPEKK composite membranes. Toimprove the proton conductivity of the SPPEKKs membranes with low DS, solid inorganicproton conductive boron phosphate is introduced into membranes in situ. process. TheSPPEKK/BPO₄ composite membranes have better conductivities while keeping the goodmechanical and thermo property, compared with pure SPPEKKs membranes. SPPEKKs withhigh DS show excellent conductivity, however they can heavily swell or even dissolve, whichrestricts the membranes from operation above a high tolerable temperature. To deal with thecontradictory, polyetherimide (PEI) is employed to blend with SPPEKK, with the attempt totake advantage of the interaction between acid and base groups of the two polymers. Resultsshow that the temperature tolerance, thermo-stability, swelling ratio, oxidative resistance andhydrolysis resistance are improved greatly, while proton conductivities go down slightly.Among the blend membranes prepared in this study, SPPEKK/PEI (90/10, w/w) is more suitable for FC application in terms of its proton conductivity and mechanical performance. Inorder to improve the performance of the blending membranes based on the aboveinvestigation, composite membranes (SPPEKK/PEI/BPO₄) have been prepared fromacid-base polymer blend and solid inorganic proton conductive BPO₄. The results show thatthe proton conductivities are improved clearly with lower swelling ratio.