Aromatic ionic monomer bearing perfluorosulfonate moiety and its polycondensation toward high performance superacid ionomers

• Synthesis of a new monomer having a superacid and two meta-polymerizable groups is studied.
• Purification of the monomer is optimized in time and technological realization.
• Polycondensation results in mixture of high- and low-molecular weight products.
• Cyclization of the chain end-groups may occur during polycondensation.
• The ionomers show good film-forming, thermo-mechanical and H+-conductive properties.

Bottom-up synthesis of perfluorosulfonic acid ionomers based on the high performance backbone is rarely performed, due to the difficulty of obtaining ionic monomers of high purity. Such an approach, however, results in ionic polymers of well-defined chemical structure and ionic group distribution. Here copper-mediated synthesis of an ionic monomer bearing a perfluorosulfonate group and two polymerizable fluorine-sites was studied. Its synthesis and purification were investigated with accuracy to find the least time-consuming and the most technologically advantageous protocol (the overall yield of the monomer consisted 76%). The monomer was subjected to polycondensation with commercial non-ionic monomers, and a series of ionomers of different ionic concentration (and thus ion exchange capacity, IEC) was obtained. The resultant ionomers demonstrated excellent film-forming properties. The obtained membranes were characterized by high glass transition temperature (>160 °C) and high proton conductivity (10−2–10−1 S/cm at 60–90 °C and 95% relative humidity). Such results make these materials promising for use in fuel cells.

Synthesis of a novel ionic monomer DFPFS bearing perfluorosulfonate moiety and its polycondensation toward polyaryl-based ionomers series P2 are reported; the high performance materials show satisfactory proton conductive properties, comparable to Nafion.Figure optionsDownload as PowerPoint slide