Linear and network polymer electrolytes based on low melting prepolymers

Abstract

Prepolymers E ₄ C ₃ E ₄ and E ₃ C ₃ E ₃ , where E represents an oxyethylene unit and C ₃ the spacer group -O(CH ₂ ) ₃ O-, were prepared by anionic polymerization of ethylene oxide using propane-1,3-diol as initiator. Oxymethylene-linking polymerization of the prepolymers gave high molar mass polymers with crystalline melting points [T _m ≈–8 °C for P(E ₄ C ₃ E ₄ ) and –16 °C for P(E ₃ C ₃ E ₃ )] and degrees of crystallinity [ca. 25% for P(E ₄ C ₃ E ₄ ) and 1% for P(E ₃ C ₃ E ₃ )] which could be related to the average E-sequence length. Inclusion of 2-methylenepropane-1,3-diol in the recipe for oxymethylene-linking polymerization gave crosslinkable polymers. Networks were obtained by photochemical crosslinking with benzophenone as sensitizer and network characteristics were determined by mechanical and swelling measurements. Linear and network polymer electrolytes were prepared by inclusion of lithium perchlorate at concentrations corresponding to O:Li=25 and O:Li=70, and conductivities were determined over the temperature range –20 to +80 °C.