In this work we present a practical thermogravimetric method for quantifying the IEC (ion exchange capacity) decrease of hydroxide exchange membranes (HEMs) during intrinsic degradation mainly occurring through nucleophilic attack of the anion exchanging group by hydroxide ions. The method involves measuring weight changes under controlled temperature and relative humidity. These conditions are close to these in a fuel cell, i.e. the measured degradation rate includes all effects originating from the polymeric structure, the consumption of hydroxide ions and the release of water. In particular, this approach involves no added solvents or base, thereby avoiding inaccuracies that may arise in other methods due to the presence of solvents (other than water) or co-ions (such as Na⁺ or K⁺). We demonstrate the method by characterizing the decomposition of membranes consisting of poly(2,6-dimethyl-1,4-phenylene oxide) functionalized with trimethyl-pentyl-ammonium side chains. The decomposition rate is found to depend on temperature, relative humidity RH (controlling the hydration number λ) and the total water content (controlled by the actual IEC and RH).

在这项工作中，我们提出了一种实用的热重分析方法，用于量化内在降解过程中氢氧化物交换膜（HEMs）的IEC（离子交换容量）下降，该降解主要是由于氢氧根离子对阴离子交换基团的亲核攻击而发生的。该方法涉及在受控温度和相对湿度下测量重量变化。这些条件接近于燃料电池中的条件，即测得的降解速率包括源自聚合物结构，氢氧根离子的消耗和水释放的所有影响。特别是，此方法不涉及添加溶剂或碱，从而避免了由于溶剂（水除外）或共离子（例如Na ⁺或K ）的存在而在其他方法中可能产生的不准确性。⁺）。我们通过表征由三甲基戊基铵侧链官能化的聚（2,6-二甲基-1,4-苯撑氧）组成的膜的分解来证明该方法。发现分解速率取决于温度，相对湿度RH（控制水合数λ）和总水分含量（由实际的IEC和RH控制）。