As described in this paper, phosphonic-acid-containing double-decker-shaped polyhedral silsesquioxane (PHOS-DDSQ) was synthesized and the proton conductivity of the PHOS-DDSQ cast film was studied under humid and non-humid conditions. To synthesize PHOS-DDSQ, double-decker-shaped polyhedral silsesquioxane (DDSQ) was initially reacted with di(ethylene glycol) (DEG) vinyl ether using hydrosilylation reaction to attach four DEG units to one DDSQ (4DEG-DDSQ). Subsequently, a phosphate esterification of hydroxyl groups in 4DEG-DDSQ was carried out using POCl3. NMR, XPS, and MALDI-TOF MS spectra and titration measurements revealed that the phosphate esterification connected two DEG units to form a crown-ether-like structure. This structure prevents hydrolysis of the phosphate ester bond. PHOS-DDSQ showed high thermal stability, with decomposition temperature exceeding 220 °C, because of its inorganic DDSQ core. A uniform film of PHOS-DDSQ can be fabricated by drop casting. The cast film showed high proton conductivity (0.12 S cm−1) under humid conditions, which is comparable to that of a Nafion® membrane. Moreover, the cast film offered good proton conductivity under non-humid conditions (3.6 × 10−4 S cm−1 at 170 °C). The conductivity and thermal stability indicate that PHOS-DDSQ is a good candidate for use as a proton-conductive membrane in hydrated type fuel cells as well as fuel cells operated at intermediate temperatures (100–200 °C) under non-humid conditions.
如本文所述,合成了含
膦酸的双十字形多面体
硅倍半氧烷(PHOS-
DDSQ),并研究了 PHOS-
DDSQ 铸膜在
潮湿和非
潮湿条件下的质子传导性。为了合成 PHOS-
DDSQ,首先使用氢
硅烷化反应将双层形多面体
硅倍半氧烷(
DDSQ)与二(
乙二醇)
乙烯基醚反应,在一个
DDSQ 上连接四个
DEG 单元(4
DEG-
DDSQ)。随后,使用 POCl3 对 4
DEG-
DDSQ 中的羟基进行
磷酸酯化反应。核磁共振、XPS 和 MALDI-TOF MS 图谱以及滴定测量结果表明,
磷酸酯化作用将两个
DEG 单元连接起来,形成了类似于
冠醚的结构。这种结构阻止了
磷酸酯键的
水解。PHOS-
DDSQ 具有很高的热稳定性,分解温度超过 220 °C,这是因为它具有无机
DDSQ 核心。PHOS-
DDSQ 的均匀薄膜可通过滴注法制造。在
潮湿条件下,铸膜显示出较高的质子传导率(0.12 S cm-1),与 Nafion® 膜的传导率相当。此外,该铸膜在非
潮湿条件下也具有良好的质子传导性(170 °C时为3.6 × 10-4 S cm-1)。质子传导性和热稳定性表明,PHOS-
DDSQ 是
水合型燃料电池以及在中间温度(100-200 ℃)和非
潮湿条件下运行的燃料电池中用作质子传导膜的理想候选材料。