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We prepared sulfonated octaphenyl polyhedral silsesquioxane (SPOSS) with its structure intact by using sulfuric acid (H2SO4) at 40 °C. We discussed the effects of sulfonation using either chlorosulfonic acid (ClSO3H) and H2SO4 on SPOSS structure and its incorporation into crosslinked sulfonated olyphenylsulfone (CSPPSU) composite polymer electrolyte membranes (PEM). An in-depth structural characterization using 29Si NMR and FTIR spectroscopies, MALDI-TOF mass spectrometry, and TGA show that phenyl loss occurred in SPOSS prepared using ClSO3H, resulting in a low ion exchange capacity (IEC) of 1.7 meq/g and a sulfonation degree (DS) of 1.9. In contrast, the phenyl remained intact in the SPOSS prepared using H2SO4. Well-dispersed 348-nm-SPOSS-H2SO4 was found to have an IEC of 2.4 meq/g and DS of 3.1. The resultant hybrid PEM of CSPPSU/SPOSS using SPOSSH2SO4 had improved swelling, mechanical and chemical strength, and conductivity. 1 wt% SPOSS-H2SO4 loading had the highest conductivity (13.7 mS/cm) at 120 °C with 40 % RH. This shows the importance of the SPOSS nanocomposite structure in dispersions in the SPPSU polymer matrix and its performance as PEM. We report on an improved direct sulfonation process at a milder condition but sulfonation yield was improved.

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• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: Polymer electrolyte membrane, Sulfonated octaphenyl polyhedral oligomeric silesquioxane, Nanocomposite, Crosslinked SPPSU/SPOSS membrane

Date published: 2024-04-08

Publisher: Elsevier BV

Journal:

• Journal of Membrane Science (ISSN: 03767388) vol. 702 122756

Funding:

• National Institute for Materials Science
• New Energy and Industrial Technology Development Organization

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4490

First published URL: https://doi.org/10.1016/j.memsci.2024.122756

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Updated at: 2024-04-24 16:42:19 +0900

Published on MDR: 2026-04-09 08:25:03 +0900