Molecular weight switchable polyurethanes enable melt processing

Preparing polymers with both high molecular weight and good processability is a continuing challenge. Herein, we report the development of molecular weight switchable polyurethane (MWSPU) containing dynamic oxime-carbamate bonds. The molecular weight of this MWSPU decreased when heated to 130 degrees C and recovered upon cooling as the result of the breaking and reformation of thermally reversible oxime-carbamate bonds. The viscosity also decreased as temperature increased, which enabled high-performance polyurethane fibres to be prepared by melt processing. This is the first study to prepare polyurethane fibres by melt spinning below the degradation temperature.