A method of producing a thermoplastic elastomer includes providing a polyether composition comprising at least a first diol terminated polyether having a number average molecular weight of 400-6000 and up to 15 wt % of fumed silica having C1-C8 alkylsilyl groups or acrylate or methacrylate ester groups at its surface, combining the polyether composition with optional additional first polyether and either a) at least one dicarboxylic acid and at least one organic diol having a molecular weight less than 250 or b) at least one dicarboxylate terminated polyamide, to form a prepolymer composition, and allowing the prepolymer composition to polymerize to form a thermoplastic elastomer.