Temperature distribution in polymer film during thermally induced phase separation (TIPS): simulations and experimental observation

Thermally-induced phase separation (TIPS) was used to fabricate polyvinylidene fluoride (PVDF) films under different quenching conditions. Temperature gradient fields were in-situ formed inside the films through varying the TIPS quenching temperature, and an enthalpy transformation method (ETM) was adopted to simulate the temperature gradient fields during the TIPS process. Our findings showed that there existed liquid–liquid phase separation (LLPS) even at higher PVDF concentration (e.g., above the monotectic point). The coexistence and competition between liquid–liquid and solid–liquid phase separations were significantly determined by the cooling rate, which helped to explain the formation mechanisms of hierarchical morphologies observed in the final TIPS films. The present work will be of substantial importance to further studies on an industrial tuning of the microstructure and performance of TIPS films through the operational parameter control.