Synthesis and characterisation of a new sulphonated hydrocarbon polymer for application as a solid proton-conducting electrolyte

•A new sulphonated hydrocarbon polymer was obtained.•Sulphonated polyindenes were obtained with a high degree of sulphonation.•The sulphonated polyindenes can be used as a polymer electrolyte.•The sulphonated polyindenes show conductivities from 10− 4 to 10− 2 S·cm− 1.•The sulphonated polyindenes exhibit thermal stability up to 200 °C.

Proton-conducting polymers were prepared by sulphonation of polyindene (PInd) with chlorosulphonic acid with various degrees of sulphonation (DSs) and characterised by 13C and 1H NMR, FTIR spectroscopy, TGA, DSC, and IES. The NMR spectra of the sulphonated polyindene (SPInd) showed only the mono-ring-substituted product at the meta-position. The SPInds are hydrophilic, and their water uptake increased with increasing DS. The SPInds exhibited 10 to 17% bound water, and samples with DSs of 21 and 96% exhibited conductivities of 10− 4 and 10− 2 S·cm− 1 at room temperature, respectively.

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