Synthesis of novel aggregating comb-shaped polyethers for use as polymer electrolytes

Polyethers having well-defined comb-shaped architectures were prepared by using poly(4-hydroxystyrene) (PHSt) as a multifunctional initiator for graft polymerization of either ethylene oxide (EO) or a mixture of EO and propylene oxide (PO). The grafting process was performed in 1,4-dioxane using NaH as ionizer for the PHSt hydroxyl groups. The precursor PHSt was prepared by first polymerizing 4-tert-butoxystyrene, using butyllithium as initiator in THF at -60 degreesC, and then deprotecting the butoxy groups. Finally, the terminal hydroxyl groups of the polyether grafts were end-capped with hexadecanoyl units through esterification. The monomer addition sequence in the graft copolymerizations with the same EO/PO feed ratio proved to have a great influence on the crystallization temperature and the crystallinity of the grafts. Also, the end-capping was found to reduce the degree of crystallinity as compared to the corresponding uncapped polymers. Solid polymer electrolytes containing lithium triflate (LiSO3-CF3) salt had ambient temperature ion conductivities of similar to 10(-5) S/cm at [Li]/[O] = 0.025. Thermal analysis of the electrolytes showed that the polymers aggregated through phase separation of the hexadecanoyl chain ends.