Summary: A series of comb‐like polysiloxanes was prepared as the base polymer for solvent‐free polymer electrolyte membranes. Hydrosilylation of poly(methylhydrosiloxane) (PMHS) was used to substitute hydrogen by the two types of side groups tetraethylene glycol allyl methyl ether and allyltrimethoxysilane (ATMS) with varying molar ratios between 5 and 40 mol‐% ATMS. The ATMS side groups served to cross‐link as‐prepared polymer electrolyte membranes after dissolving lithium trifluoromethylsulfonate (triflate) or lithium bis(trifluoromethylsulfonyl)imide. The ionic conductivities of these salt‐in‐polymer membranes prepared with a constant concentration of 10 wt.‐% lithium triflate showed a maximum conductivity of 4.6 × 10?5 S · cm?1 at 30 °C for 10 mol‐% ATMS substitution. In another series of experiments with the ATMS substitution held constant at 10 mol‐%, the salt concentration was varied yielding a maximum conductivity of 1.4 × 10?4 S · cm?1 at 30 °C for 12.5 wt.‐% lithium triflate.
