【作者】 王刚；

【导师】 颜德岳； 肖谷雨；

【作者基本信息】 上海交通大学 ， 高分子化学与物理， 2012， 博士

【摘要】 质子交换膜燃料电池是一种清洁能源利用装置，其质子交换膜是它的核心部件之一。目前广泛使用的质子交换膜是Nafion膜，具有高温和低湿度下电导率低、甲醇渗透率高和价格昂贵等缺点。为了克服这些缺点，越来越多的研究转向开发新型的芳香族质子交换膜。磷酸掺杂的聚苯并咪唑质子交换膜具有在高温下良好的电导率、电渗曳力系数几乎为零和甲醇渗透率低的优点而引起人们的广泛关注。随后开展了磺化聚苯并咪唑质子交换膜的研究，通常采用后磺化、接枝和直接缩聚三种方法来制备磺化聚苯并咪唑质子交换膜。其中，直接缩聚法能够将各种具有优良性质的官能团结合到聚合物分子结构中，从而使产物具有良好的综合性能。另一方面，磺化聚苯并咪唑由于其刚性棒状的主链结构和分子间酸碱相互作用而具有很差的溶解性，一般难以制备成质子交换膜。近年来，本课题组通过将柔性基团或大侧基引入到聚合物主链来增加聚合物的柔顺性或提高聚合物分子间的间距，打乱聚合物分子链的规整排列，从而提高产物的溶解性，制备了一系列的可溶性磺化聚苯并咪唑。本文通过缩聚反应将不对称的1,4-萘单元引入到磺化聚苯并咪唑主链，打乱其分子链的规整排列，提高产物的溶解性。另外，将苯磺酸大侧基和氧膦基团同时引入磺化聚苯并咪唑来增加聚合物主链分子间的间距，打乱聚合物分子的规整排列，制备了一系列的含氧膦基团的可溶性磺化聚苯并咪唑。磺化聚苯并噻唑是一类性能优良的质子交换膜基体材料。最初磺化聚苯并噻唑只能用做结构材料，由于其极差的溶解性和难以得到高分子量的聚合物而不能制备质子交换膜。本课题组采用双(3-磺酸钠-4-羧基苯基)砜通过直接缩聚法制备了三个系列的高分子量的可溶性磺化聚苯并噻唑，并首次制备了可溶性磺化聚苯并噻唑质子交换膜。对比研究表明，引入六氟异亚丙基柔性基团和苯磺酰大侧基能够显著提高磺化聚苯并噻唑的溶解性。本文分别采用3,3’-二磺酸钠-4,4’-二羧基联苯、6-磺化-1,4-二羧基萘和2,2’-二磺酸钠-4,4’-二羧基二苯醚三个磺化二羧酸单体通过直接缩聚法制备了三种新型结构的磺化聚苯并噻唑。并通过引入柔性的六氟异亚丙基或二苯醚基团来增加磺化聚苯并噻唑分子链的柔顺性，从而提高产物的溶解性。本文第二章制备了含不对称的1,4-萘单元的磺化聚苯并咪唑质子交换膜。首先，合成了6-磺酸钠-1,4-二羧基萘(SNAA)和6,8-二磺酸钠-1，4-二羧基萘(DSNAA)两个不对称的二羧酸单体。将单磺化单体SNAA缩聚制备了单磺化聚苯并咪唑。再采用二磺化单体DSNAA通过直接缩聚法制备了其他四种双磺化聚苯并咪唑。不对称1,4-萘单元的引入打乱了聚合物主链的规整排列，有效地改善了磺化聚苯并咪唑的溶解性，产物在NMP，DMF和DMSO等溶剂中具有良好的溶解性，可以采用溶液浇铸法制备出透明、韧性的膜。该两类磺化聚苯并咪唑质子交换膜在90350oC温度范围内无熔融、结晶及玻璃化转变，热降解5%的温度高于410oC，热稳定性高，并且其耐氧化性和力学性能优异。该sPBI膜在80oC的吸水率在29.932.9%范围，这很接近Nafion117在同样温度下的吸水率(30%)；它们在80oC的溶胀率在8.89.3%之间，这比Nafion117在同样温度下的溶胀率(20%)的一半还低。由于咪唑基团和磺酸基团的相互作用，该sPBI膜的质子电导率较低，但是sPBI膜在高温下电导率较高或者可以通过掺杂等手段来改善。AFM相图表明，双磺化sPBI膜亲水相的尺寸和连贯性随磺化度的增加而增加，同时其电导率和吸水、溶胀率等也随磺化度的增加而增加；在具有相同IEC时，sPBI-N100膜的亲水相比双磺化的sPBI膜连贯性更好，因此，前者具有最高的吸水率、溶胀率和电导率。第三章制备了含氧膦基团的磺化聚苯并咪唑质子交换膜。本章首先制备了磺化二(4-甲酸甲酯基苯基)苯基氧膦单体(sMBPO)，然后用sMBPO通过直接缩聚法制备了含氧膦基团的磺化聚苯并咪唑(sPBI-P)。苯磺酸大侧基和氧膦单元被同时引入到了sPBI-P分子链，有效地增加了聚合物分子的间距，打乱了聚合物分子的规整排列，提高了产物的溶解性，可以用溶液浇注法制备质子交换膜。与此同时，氧膦单元的引入还增加了sPBI-P的保水性，在具有同样IEC时，sPBI-P膜的吸水率比sPBI的吸水率增加了39%。sPBI-P还具有很好的热稳定性、氧化稳定性和力学性能。但是和其他磺化聚苯并咪唑相似，sPBI-P膜电导率较低，这可以用掺杂等手段进行改善。第四章制备了含磺化联苯单元的聚苯并噻唑质子交换膜。通过3,3’-二磺酸钠-4,4’-二羧基联苯和4,4’-二羧基联苯或2,2-双(4-羧基苯基)六氟丙烷(6FA)缩聚合成了两个系列的磺化聚苯并噻唑，分别命名为sPBT-DP和sPBT-BP。对比研究表明，引入六氟异亚丙基柔性基团能够显著提高磺化聚苯并噻唑分子链的柔顺性，提高产物的溶解性。sPBT-BP膜具有高的热稳定性，氧化稳定性和优异的力学性能。sPBT-BP膜还具有高的质子电导率和低的溶胀率。例如，在80oC时sPBT-BP57.5的质子电导率为0.094S/cm，水平方向的溶胀率为9.7%，厚度方向的溶胀率为35%。另外，其吸水率、水平方向和厚度方向的溶胀率都随温度升高而增加很少。第五章制备了含1,4-萘单元的磺化聚苯并噻唑质子交换膜。用2,5-二氨基-1,4-苯二硫醇二盐酸盐、6-磺化-1,4-二羧基萘、1,4-二羧基萘或2,2-双(4-羧基苯基)六氟丙烷通过直接缩聚法合成了两个系列的磺化聚苯并噻唑，分别命名为sPBT-NA和sPBT-6F。sPBT-NA不溶于一般溶剂，而sPBT-6F由于柔性基团的引入能够溶于DMSO。所有的sPBT-6F膜都具有高的热稳定性、氧化稳定性和优异的力学性能。它们还具有合适的吸水率和水平、厚度两个方向的溶胀率。例如，在80oC时sPBT-6F70的吸水率为34%，水平和厚度方向的溶胀率分别为4.4%和44.5%，这也小于或接近Nafion117在相同温度下的吸水率和溶胀率。其中特别值得一提的是，sPBT-6F70膜的吸水率和水平、厚度方向的溶胀率在2590oC范围内几乎保持不变，这种情况鲜有报道。DMA的数据表明，sPBT-6F膜的储能模量在180oC之前都没有减小，同时它们在80oC左右具有一个次级转变，这种次级转变可能造成膜中的磺酸基团和碱性的噻唑基团相对位置和距离的改变，而形成强烈的酸碱分子间相互作用，从而使储能模量增加。同时，这些分子间强烈的相互作用能够促使sPBT-6F膜具有较低的溶胀率。sPBT-6F膜还具有高的电导率，如sPBT-6F90膜的电导率接近Nafion117电导率的两倍。另外，sPBT-6F80,sPBT-6F85和sPBT-6F95膜的电导率也高于Nafion117的电导率。第六章制备了含磺化二苯醚单元的聚苯并噻唑质子交换膜。通过2,5-二氨基-1,4-苯二硫醇二盐酸盐、2,2’-二磺酸钠-4,4’-二羧基二苯醚和4,4’-二羧基二苯醚或2,2-双(4-羧基苯基)六氟丙烷缩聚制备了两个系列的可溶性磺化聚苯并噻唑(sPBT-PE和sPBT-6F)。对比研究表明，引入二苯醚单元能够有效地增加聚合物主链的柔顺性，改善产物的溶解性；引入六氟异亚丙基更能有效地增加聚合物主链的柔顺性，使产物具有更好的溶解性。sPBT-PE和sPBT-6F膜都具有高的热稳定性、氧化稳定性和优异的力学性能。另外，它们还具有高的质子电导率和卓越的尺寸稳定性。例如，在80oC时，它们的质子电导率范围是0.11–0.13S/cm，在98oC时它们的水平方向的溶胀率仅为14–15%，厚度方向的溶胀率仅为7.1–30%。同样地，sPBT-PE和sPBT-6F膜在2590oC的吸水率和水平、厚度的溶胀率也几乎保持不变，这也可能是这些分子间强烈的相互作用引起的。因此，这些噻唑基团可以被用作降低质子交换膜溶胀率的新型结构基团，通过它们可以设计低溶胀率的质子交换膜。与sPBT-6F系列相比，在具有相等的IEC时, sPBT-PE系列具有更高的质子电导率，更低的溶解性和断裂伸长率。更多还原

【Abstract】 Proton exchange membranes fuel cells (PEMFCs) are one of the most attractivedevices as the clean power sources. Proton exchange membranes (PEMs) are one ofthe key components of PEMFCs. At present, Nafion, which is extensively used asPEMs has some disadvantages, such as the serious loss of proton conductivity underlow humidity or high temperature, high methanol permeability, and high cost. Toovercome those drawbacks, the main focus is on developing aromatic PEMs.H3PO4-doped polybenzimidazole membranes exhibited wonderful properties suchas an electro-osmotic drag number nearly approaching zero, high proton conductivityat elevated temperatures, and low methanol permeability. Thepolybenzimidazole-based PEMs have attracted particular attention. Sulfonatedpolybenzimidazole (sPBI) membranes have been developed after that, in order toattach the ionic groups to PBI backbone by chemical linkage, the grafting,post-sulfonation, and direct-polycondensation methods have been developed toprepare sPBI membranes. The direct-polycondensation method shows the advantagesby combination of various functional groups, resulting in excellent comprehensiveproperties of the products. On the other hand, the rigid-rod backbone andintermolecular acid-base interactions of sulfonated polybenzimidazoles often makethem poorly soluble and difficult to form membranes used as PEMs. Recently, theflexible moieties or bulky pendant groups were incorporated into the backbone ofsPBI in order to enhance the flexibility or disrupt the regular packing of polymerchains and thus to improve the solubility by our group. We have synthesized a seriesof sulfonated polybenzimidazoles. In this paper, the asymmetric1,4-naphthalenegroup was incorporated into the backbone of sPBI in order to disrupt the regularpacking of polymer chains and thus to prepare soluble sPBI. Moreover, bothbenzenesulfonic acid bulky pendant groups and phosphine oxide groups wereincorporated into the backbone of sPBI in order to increase the distance betweenpolymer chains and disrupt the regular packing of polymer chains, and then to improve the solubility of sPBI.Sulfonated polybenzoxazoles are a kind of high performance matrix materials ofPEMs. They were initially designed to be used as structural materials, which cannotbe used as PEM because of their low molecular weight or poor solubility. Three seriesof sulfonated polybenzothiazoles were prepared by polycondensation ofbis(3-sulfonate-4-carboxyphenyl) sulfone by our group. We have also developedhighly soluble sPBT as PEMs with high molecular weight for the first time. As shownin a comparison research, the incorporation of the flexibile hexafluoroisopropylideneunits and sulfophenyisulfonyl pendant groups could obviously enhance the solubilityof sulfonated polybenzoxazoles. In this paper, three series of sulfonatedpolybenzothiazoles were prepared by polycondensation of3,3’-disulfonate-4,4’-dicarboxylbiphenyl(SCBP),6-sulfonate-1,4-naphthalene dicarboxylic acid(SNAA), and bis(2-sulfonate-4-carboxyphenyl) ether, respectively. The flexiblehexafluoroisopropylidene units and diphenyl ether groups were incorporated into thebackbone of sPBT in order to enhance the flexibility or disrupt the regular packing ofpolymer chains.In Chapter2, soluble sulfonated polybenzimidazoles (sPBI) as proton exchangemembranes using asymmetric dicarboxylic acid monomers was synthesized. Firstly,6-sulfonate-1,4-naphthalene dicarboxylic acid (SNAA) and6,8-disulfonate-1,4-naphthalene dicarboxylic acid (DSNAA), were designed andsynthesized. Subsequently, mono-sulfonated polybenzimidazoles (sPBI-N100) weresynthesized by polycondensation of SNAA. Other four series of sulfonatedpolybenzimidazoles were also prepared by copolymerization of DSNAA. Theincorporation of the asymmetric1,4-naphthalene group enhanced the asymmetry ofpolymer chains and disrupted their regular packing. These sPBI ionomers thusexhibited excellent solubility in NMP, DMF and DMSO, so they could be cast to themembranes as PEMs. Those two series of sPBI showed high thermal stability, sPBIdisplayed a Td5above410oC and no glass transition in their DSC thermograms at thetemperature of90–350oC. Moreover, sPBI membranes showed excellent oxidativestability. The water uptake of those sPBI membranes is in the range of29.932.9%at 80oC, very close to that (30%) of Nafion117; their swelling ranges from8.8%to9.3%at80oC, which is less than half that (20%) of Nafion117. However, they displayedlow proton conductivity like other sPBI because of the acid-base interactions betweenthe sulfonic acid and benzimidazole moieties. As shown in AFM images, theconnectivity and width of hydrophilic domains of dual sPBI membranes increase withincreasing sulfonation degree. At the same time, the water uptake, swelling, andproton conductivity are also increased with increasing sulfonation degree. In addition,sPBI-N100with the lowest IEC showed the highest proton conductivity among all thesPBI. This is because it displayed more connected hydrophilic domains than any othersPBI.In Chapter3, soluble sulfonated polybenzimidazoles (sPBI-P) as proton exchangemembranes with phosphine oxide was synthesized. Sulfonate bis(4-methyl benzoate)phenyl phosphine oxide (sMBPO) was synthesized. Soluble sulfonatedpolybenzimidazoles phosphine oxide (sPBI-P) was prepared using sMBPO. Bothbenzenesulfonic acid bulky pendant groups and phosphine oxide groups wereincorporated into the backbone of sPBI in order to disrupt the regular packing ofpolymer chains and then improve the solubility of sPBI. As sPBI-P is soluble inDMSO, they could be cast into homogeneous membrane as PEMs. Incorporation ofthe phosphine oxide groups to the backbone enhanced the water-keeping ability ofsPBI-P. sPBI-P membranes with the same IEC showed39%more water uptake thanthat of other sPBI. They also showed high thermal, oxidative stability and excellentmechanical properties. However, they displayed low proton conductivity like othersPBI because of the acid-base interactions between the sulfonic acid andbenzimidazole moieties. But their proton conductivity could be improved by thedoping or blending method.In Chapter4, soluble sulfonated polybenzothiazoles as proton exchange membraneswith biphenyl group was synthesized. Two series of sulfonated polybenzothiazoles bypolycondensation of2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) and3,3’-disulfonate-4,4’-dicarboxylbiphenyl (SCBP) with4,4’-dicarboxylbiphenyl(DCBP) or2,2-bis(4-carboxyphenyl) hexafluoropropane (6FA), respectively. The first series was expressed as sPBT-DP, while the other series was denoted as sPBT-BP.Contrast research shows that the flexible hexafluoroisopropylidene moieties wereincorporated into the backbone of sPBT in order to disrupt the regular packing andenhance the solubility. The sPBT-BP series showed high thermal and oxidativestability as well as excellent mechanical properties. Moreover, the sPBT-BPmembranes exhibited high proton conductivity and outstanding dimensional stability.For example, sPBT-BP57.5displayed a proton conductivity of0.094S/cm, anin-plane swelling of9.7%and a through-plane swelling of35%. Additionally, thewater uptake, in-plane swelling, and through-plane swelling of sPBT-BP membranesincreased only slightly with increasing temperature because of strong intermolecularinteractions.In Chapter5, soluble sulfonated polybenzothiazoles as proton exchange membraneswith1,4-naphthalene group was developed to synthesized. Two series of sulfonatedpolybenzothiazoles (sPBT) were synthesized by polycondensation of6-sulfonate-1,4-naphthalene dicarboxylic acid (SNAA),2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) and1,4-naphthalenedicarboxylic acid (NA) or2,2-bis(4-carboxyphenyl) hexafluoropropane (6FA),respectively. The first series was expressed as sPBT-NA, while the other series wasdenoted as sPBT-6F. The sPBT-NA series are insoluble in common solvents, sPBT-6Fseries are soluble in DMSO due to the incorporation of the flexiblehexafluoroisopropylidene moieties onto polymer chains. sPBT-6F showed highthermal and oxidative stability as well as excellent mechanical properties. Moreover,they showed appropriate water uptake and swelling in plan and thickness. Forexample, sPBT-6F70displayed a water uptake of34%, an in-plane swelling of4.4%and a through-plane swelling of44.5%at80oC, this is less than half that (20%) ofNafion117. Especially, the water uptake and swelling of sPBT-6F70almost remainsunchanged in the range of25–90oC. The storage modulus of sPBT-6F membranesalmost exhibited an increasing trend up to180oC. sPBT-6F membranes showed asecondary relaxation at around80oC. It could cause the membrane to change therelative place of the sulfonic acid and the basic benzothiazole group as well as thedistance between them, thus forming stronger intermolecular acid-base interactions and facilitating the increase of storage modulus. These strong intermolecularinteractions could facilitate the sPBT-6F membranes to resist the swelling. ThesesPBT-6F membranes also show high proton conductivity, the proton conductivity ofsPBT-6F90showed almost twice that of Nafion117, and the proton conductivity ofsPBT-6F80, sPBT-6F85and sPBT-6F95is also as high as that of Nafion117.In Chapter6, soluble sulfonated polybenzothiazoles as proton exchange membraneswere synthesized by incorporation of flexible diphenyl ether groups to the backbone.2,5-Diamino-1,4-benzenedithiol dihydrochloride, bis(2-sulfonate-4-carboxyphenyl)ether, and bis(4-carboxyphenyl) ether or2,2-bis(4-carboxyphenyl) hexafluoropropanewere polycondensated to synthesize sPBTs (sPBT-PE and sPBT-6F). As shown in thecomparison study, the incorporation of flexible diphenyl ether groups into thebackbone of sPBT could disrupt the regular packing and enhance the solubility; theflexible hexafluoroisopropylidene moieties were incorporated into the backbone ofsPBT, which could enhance the flexibility of the polymer chains and then highlyincrease the solubility. Both series sPBTs show high thermal and oxidative stability aswell as excellent mechanical properties. Furthermore, both of them exhibited highproton conductivity and outstanding dimensional stability. For example, theydisplayed a proton conductivity of0.11–0.13S/cm at80oC, but only exhibited anin-plane swelling of14–15%and a through-plane swelling of7.1–30%even at98oC.Equally importantly, their in-plane and through-plane swelling almost showed nochange with increasing temperature because of strong intermolecular interactions. Thebenzothiazole units thus could be regarded as a new structural unit to fabricate theswelling of PEMs, facilitating to design low-swelling PEMs. Compared with thesPBT-6F series, the sPBT-PE series with an equal IEC displayed higher protonconductivity but lower solubility and elongation at break.更多还原