Phase change solvents for thermoplastic polymers to provide blended compositions. Above the phase change temperature of the solvent, the phase change solvent solubilizes or intimately mixes with the thermoplastic polymer. Below the phase change temperature of the solvent, the phase change solvent solidifies or crystallizes within the thermoplastic matrix. The phase change behavior of these materials produce blended compositions that exhibit lowered shear viscosity and lowered processing temperature without substantially compromising mechanical properties of the thermoplastic polymer. The present invention also relates to a method of improving the processability of a thermoplastic polymer using the phase change solvent.