Proton-conducting, thermally and electrochemically stable, heterocycle-grafted polysiloxanes have been synthesized via hydrosilylation of vinyl or allyl functionalized weakly basic heterocyclic motifs with a polymethylhydrosiloxane precursor. The basicity of the amphoteric heterocycles was tuned by introducing electron-withdrawing groups, whose presence also produced a decrease in the polymers' glass transition temperature. The proton conductivity depended strongly on the T g of the polymer matrix and the volume fraction of proton carriers, while the effect of reducing the pK a of the heterocycle was less pronounced. The resulting polymers showed the highest reported proton conductivities of up to 0.1 mS/cm at temperatures below 80 °C and up to 5 mS/cm at 180 °C when doped with trifluoroacetic acid.

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