新型磺化聚苯并噻唑质子交换膜的合成和表征

Proton exchange membrane fuel cells (PEMFCs) are one of the most attractive devices as one kind of clean power sources. Proton exchange membranes (PEMs) are one of the key components of PEMFCs. At present, Nafion, which is extensively used as PEMs has some disadvantages, such as the serious loss of proton conductivity under low humidity or high temperature, high methanol permeability, and high cost.Sulfonated polybenzoxazoles are a kind of high performance matrix materials of PEMs.However,sulfonated polybenzoxazoles cannot be used as PEMs because of their poor solubility or low molecular weight.Highly soluble sPBT as PEMs with high molecular weight were developed from this paper.At first,both benzenesulfonic acid bulky pendant groups and phosphine oxide groups were incorporated into the backbone of sPBT in order to disrupt the regular packing of polymer chains and then improve the solubility of sPBT.Secondly,the incorporation of the asymmetric naphthalene group with mono-sulfonated or double-sulfonated monomers enhanced the asymmetry of polymer chains and disrupted their regular packing.At the same time,flexible diphenyl ether groups and hexafluoroisopropylidene moieties were incorporated into the backbone of sPBT in order to enhance the flexibility of polymer chains.As a result,the solubility of sPBT can ben improved greatly.Finally,sulfonated polybenzothiazoles with benzimidazole moieties containing side soulfonated chain were successfully prepared by polycondensation.Sulfonated side chains were incorporated into the backbone of polymer in order to disrupt the regular packing of polymer chains and then improve the solubility of sPBT.Incorporating the benzimidazole moieties can improve the mechanical properties,oxidative stability and so on.Side chain reaction can eliminate the acid–base interactions between the benzimidazole and sulfonic acid groups to improve the proton conductivity.

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。Nafion膜是目前广泛使用的质子交换膜，它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。磺化聚苯并噻唑(sPBT)是性能优良的质子交换膜基体材料。但是由于其极差的溶解性和较低的分子量而很难制备质子交换膜。本文制备一系列可溶性sPBT质子交换膜。首先，把苯磺酸和氧膦大侧基同时引入到sPBT分子链，增加了分子间距，打乱了分子链的规整排列，提高了溶解性。其次，单磺化和双磺化的不对称萘单元的引入打乱了主链的规整排列，同时把二苯醚或六氟异亚丙基柔性基团分别引入到sPBT主链，增加了主链的柔顺性，从而更好地增加了溶解性。最后，制备含磺酸基支链的含咪唑基团的磺化聚苯并噻唑，磺酸基支链打乱了主链的规整排列，增加了溶解性。引入咪唑基团提高机械性能和氧化稳定性等，支化反应消除磺酸基团和咪唑单元的酸碱相互作用，增加了电导率。

磺化聚苯并噻唑(sPBT)是一种性能优良的质子交换膜基体材料。本文从分子设计的角度出发，设计合成了几个系列可溶性sPBT质子交换膜。首先，合成了两个系列的含60% 和70%磺化度的无规磺化聚苯并噻唑-咪唑质子交换膜（sPBT-BI）。引入BI基团极大地提高了sPBT-BI的力学性能，sPBT-BI70-10膜的拉伸强度是125 Mpa，断裂伸长率是38.9%，它们分别比sPBT膜提高了56.5% 和145%。sPBT-BI的溶解性、热稳定性和耐氧化性也都有所提高。在AFM 相图和TEM图中sPBT-BI膜的离子簇都随BI基团含量的增加而变窄。这导致其溶胀率降低、力学性能增加、质子电导率减少。引入5% 的BI基团有效地增加了PEMFC H2/空气单电池性能和耐久性。其次，分别用2,5-二氨基-1,4-苯二硫醇二盐酸盐 (DABDT)、4,8-二磺酸基-2,6-二羧基萘 (DSNA)和2,2-双(4-羧基苯基)六氟丙烷 (6FA)或2,6-二羧基萘(NA)制备了两个系列的含有萘基团的无规共聚sPBT。同时引入萘基团和柔性六氟异亚丙基增加了sPBT的溶解性。sPBT-6FA膜具有优异的尺寸稳定性、高的热稳定性和氧化稳定性、良好的力学性能和高的质子电导率。再次，用2,5-二氨基-1,4-苯二硫醇二盐酸盐 (DABDT)、6-磺化-1,4-二羧基萘(NA)、1,4-二羧基萘或2,2-双(4-羧基苯基)六氟丙烷 (6FA) 通过直接缩聚法制备两个系列的磺化sPBT。sPBT-NA在一般的溶剂中不溶， sPBT-6F可以在极性溶剂中溶解。表明把柔性基团引入聚合物主链比不对称基团引入聚合物主链对增加聚合物的溶解性贡献大。sPBT-6F具有高的质子电导率、热稳定性和氧化稳定性、良好的力学性能和合适的吸水率和溶胀率。最后，制备了二(4-甲酸甲酯基苯基)苯基氧膦(MBPO)和磺化二(4-甲酸甲酯基苯基)苯基氧膦(sMBPO)单体，并用1H NMR,13C NMR,13C dept135 NMR 和FT-IR确认了结构,用MBPO和sMBPO制备了sPBTs 和 sPBIs。