【作者】 李秀平；

【导师】 蹇锡高； 刘程；

【作者基本信息】 大连理工大学 ， 高分子化学与物理， 2013， 博士

【摘要】 聚苯并咪唑(PBI)因具有优异的耐热性、机械性能和耐化学腐蚀性,在航空航天、电子电气和汽车机械等行业具有广阔的应用前景。然而,传统PBI难溶解亦难熔融,加工成型困难,限制了其在质子交换膜燃料电池等领域的应用。本文将扭曲、非共平面的杂萘联苯结构引入到PBI的主链中,旨在获得既耐高温又可溶解的新型聚苯并咪唑,进而制备其质子交换膜,研究其质子交换膜的性能。以4-[4-(4-羧基苯氧基)苯基]-2-(4-羧基苯基)二氮杂萘-1-酮(CPPBC)和联苯四胺(DAB)为单体,以多聚磷酸(PPA)为溶剂合成了主链含杂萘联苯结构的聚苯并咪唑PPBI。通过对模型化合物的波谱分析和分子模拟,展现了PPBI重复结构单元的扭曲结构。所合成PPBI的特性粘度达到1.78dL/g,易溶于DMSO、NMP和DMAc等极性非质子有机溶剂,其溶解性优于传统的间苯型m-PBI和对苯型p-PBI。广角X射线衍射(WAXD)测试结果表明PPBI呈无定形态。PPBI具有优异的热稳定性,玻璃化转变温度为402℃,5%的热失重达550℃,在800℃的残碳率为58.3%。以DAB、CPPBC和对苯二甲酸(TPA)为单体,PPA为溶剂,设计合成了一系列主链含杂萘联苯结构和对苯结构的聚苯并咪唑p-PPBI三元共聚物。采用红外光谱与核磁共振表征了聚合物结构,WAXD测试结果表明p-PPBI呈无定形结构。p-PPBI的特性粘度可达3.43dL/g,在NMP、DMAc和DMSO中具有良好的溶解性。p-PPBI具有优异的热性能,玻璃化转变温度高达426℃,5%的热失重高达564℃,800℃的残碳率高达75.7%。p-PPBI拉伸强度可达98.8MPa。为赋予PBI质子传导性能,以DAB、CPPBC和5-磺酸钠间苯二甲酸(SIPN)为单体,PPA为溶剂,合成并制备了一系列磺化度可控的含杂萘联苯结构磺化聚苯并咪唑SPPBI质子交换膜。由红外光谱与核磁共振表征了SPPBI的结构。WAXD测试表明SPPBI呈无定形态。SPPBI膜具有较低的吸水率和溶胀率,离子交换容量(IEC)可达0.76meq/g,80℃水中的质子传导率可达1.3×10-2S/cm,甲醇渗透系数可低至5.46×10-10cm2/s,拉伸强度可达48.2MPa。SPPBI膜在Feton试剂中经过120h测试均未出现破裂,耐水解性测试后依然保持良好的机械强度。与Nafion(?)117相比,SPPBI膜具有更优异的拉伸强度和阻醇性能(甲醇渗透系数比Nafion(?)117低约4个数量级)。其吸水率、溶胀率、IEC值和质子传导率随着磺化度的增大而增大,其阻醇性能、耐氧化性和耐水解性随着杂萘联苯结构含量的增大而增强,可通过调节SPPBI的结构,实现对膜性能的调控。为制备高温使用具有高质子传导率的含杂萘联苯结构PBI质子交换膜,将PPBI与p-PPBI膜进行磷酸掺杂,制备了磷酸掺杂含杂萘联苯结构聚苯并眯唑膜,并对其性能进行了研究。考察了磷酸浓度、掺杂温度和掺杂时间对膜性能的影响,优化了掺杂条件。此系列膜在14.7mol/L磷酸中180℃下掺杂30h以上能获得掺杂度高达15.2molH3PO4的磷酸掺杂膜。所得掺杂膜的质子传导率随掺杂度的增大而增大,PPBI膜的质子传导率在高温无水的条件下可达0.13S/cm。掺杂后此系列膜拉伸强度可达26.1MPa,在Feton试剂中开始破裂时间可长达81h。为制备具有更好质子传导性能和耐氧化性的磷酸掺杂含杂萘联苯结构PBI膜,以DAB、CPPBC和2,5-羟基对苯二甲酸(TPA-OH)为单体,PPA为溶剂,合成了一系列含羟基和杂萘联苯结构的聚苯并咪唑PPBIOH。经反应溶液直接铺膜法制备了其磷酸掺杂膜,并优化了制膜工艺。PPBIOH能溶解在浓硫酸和NMP中,特性粘度可达2.10dI/g。PPBIOH膜在高温无水条件下质子传导率可高达0.22S/cm,在Feton试剂中的开始破裂时间可长达155h,其拉伸强度能够满足质子交换膜的应用要求。更多还原

【Abstract】 Polybenzimidazole (PBI) is one of the classes of aromatic heterocyclic polymers, which have high mechanical properties, excellent thermal stability and chemical resistance. Because of these outstanding comprehensive properties, they have been widely used in automotive industry, aeronautical industry, microelectronics industry, fuel cells components, etc. However, the major drawback of PBI is their extreme processing conditions due to the poor solubility and infusibility. Phthalazinone moiety is a heterocyclic, crank and twisted, non-coplanar and asymmetrical structure, which can reduce the regularity of the main chain, cumber the close packing of chains and increase the free space between the molecular chains, and thus enhance the solubility of polymers.In this study, novel serieses of polybenzimidazoles containing phthalazinone moiety in the polymer main chain have been synthesized. Their applications in proton exchange membrane fuel cells have been studied.A novel polybenzimidazole containing phthalazinone structure (PPBI) was synthesized from4-(4-(4-(4-carboxyphenoxy)phenyl)-1-oxophthalazin-2(1H)-yl)benzoic acid (CPPBC) and3,3’-diaminobenzidine (DAB) by solution polycondensation in polyphosphoric acid (PPA). Furthermore, the model compound of PPBI was synthesized. The chemical structure of the model compound was established by FT-IR and NMR. To provide further insight into the fundamentals of molecular architecture, molecular simulation was carried out for the model compound containing phthalazinone moiety. The PPBI polymer was found to be soluble in aprotic polar solvents such as NMP, DMAc, and DMSO. The PPBI had inherent viscosity of1.78dL/g, and showed amorphous nature as evaluated by WAXD. PPBI had high glass transition temperatures of402℃and excellent thermal stability with the temperatures for5%polymer weight loss of550℃and char yields at800℃of58.3%.A novel series of polybenzimidazoles containing4-phenyl phthalazinone moieties and p-phenylene linkages (p-PPBI) were synthesized from CPPBC, terephthalic acid (TPA) and DAB in PPA. The chemical structures of p-PPBI polymers were characterized by FT-IR and NMR. The p-PPBI exhibited amorphous nature as evaluated by WAXD. The resultant polymers had inherent viscosity up to3.43dL/g and showed good solubility in NMP, DMAc and DMSO. The p-PPBI exhibited high glass transition temperatures of426℃and excellent thermal stability with the5%weight loss temperatures of564℃. The highest char yield of p-PPBI at800℃was75.7%. Moreover, the tensile strength of p-PPBI was up to98.8MPa. A novel series of sulfonated4-phenyl phthalazinone-based polybenzimidazoles (SPPBI) were synthesized by solution polycondensation of DAB, CPPBC and5-sulfoisophthalic acid monosodium salt (SIPN) in PPA. Their chemical structures were characterized by NMR, FTIR and WAXD. The SPPBI membranes were prepared by solution casting technique, displaying low water uptake and swelling ratio. The SPPBI membranes present IEC value up to0.76meq/g. The SPPBI membranes had unexpected low methanol permeability (5.46×10-10cm2/s, almost4order of magnitudes lower than Nafion(?)117), and their proton conductivities were comparable with Nafion(?)117at the temperature below100℃(～1.3×10-2S/cm at80℃in water). The sulfonation degree (SD) as well as the properties of SPPBI membranes can be controlled. The water uptake, swelling ratio, IEC value and proton conductivity increased with the increasing of SD, while the methanol permeability, oxidative stability and hydrolysis resistance were enhanced with the increasing phthalazinone content.To prepare PBI membranes with high proton condcutivity, the amorphous PPBI and p-PPBI polymers were cast into membranes, doped with phosphoric acid and further investigated as proton exchange membranes. To modify the doping conditions, the PPBI membranes were doped in PA with different concentration, at different doping temperature and for different time. Membranes with high acid doping level (-15.2mol H3PO4) and high proton conductivity (～0.13S/cm in anhydrous condition) were obtained after doping with14.7mol/L phosphoric acid at180℃for30h. These obtained membranes present breaking time up to81h in Feton regent and tensile strength up to26.1MPa.To prepare PA doped PBI membranes with higher conductivity as well as better oxdative stability, a series of novel polybenzimidazoles containing4-phenyl phthalazinone moieties and hydroxyl groups (PPBIOH) were synthesized from CPPBC,2,5-dyhydroxyterephthalic acid (TPA-OH) and DAB in PPA. The resultant polymers showed good solubility in H2SO4and NMP. The inherent viscosity of the polymers was up to2.10dL/g. The corresponding acid doped membranes were prepared directly from the polymerization solution by the PPA process. These membranes showed high proton conductivities up to0.22S/cm at high temperature under anhydrous condition. The breaking time in Feton regent was up to155h and the tensile strength was enouth for PEM use.更多还原