Multiscale simulation on the membrane formation process via thermally induced phase separation accompanied with heat transfer

A novel methodology based on dissipative particle dynamics (DPD) simulation and the results of macroscopic mathematical models was established to obtain multiscale understanding on the membrane formation process via thermally induced phase separation (TIPS) method accompanied with heat transfer between the polymer solution and coagulation bath, taken into account polyvinylidene fluoride - diphenyl carbonate (PVDF-DPC) system. The phase separation process simulated by this methodology could be close to a real membrane formation process by adopting a linear cooling algorithm based on the macroscopic model results and providing much larger scales. The simulation results indicated that the temperature gradient in the polymer solution resulted from the heat transfer at the polymer solution-coagulation bath interface had a significant influence on the phase separation process, thereby different parts in the polymer solution possessed different cooling rates and coarsen time, which resulted in a microporous membrane with anisotropic structure. Secondly, as the polymer concentration increased, the system became much denser and the phase separation rate got lower due to a decline in the flexibility of the system. The results proved that a further deep understanding could be obtained by this methodology.