Computer simulations on double hydrophobic PS-b-PMMA porous membrane by non-solvent induced phase separation

Abstract

The formation of porous membrane of double hydrophobic Polystyrene-b-Poly (methyl methacrylate) (PS-b-PMMA) block copolymer is studied by dissipative particle dynamics (DPD) simulations with the non-solvent induced phase separation (NIPS) method. It is also the first time to investigate the mechanism for double hydrophobic copolymer to form porous membrane. Results show that polymer concentration has the most significant effect on the membrane morphology. Different polymer concentrations lead to diversified morphologies. For the double hydrophobic PS-b-PMMA system, although PS and PMMA are both hydrophobic, due to their relative difference in hydrophobicity, the polymer and non-solvent undergo micro-phase separation. Channel membrane could be observed among the polymer concentration range of 30~40%. The block ratio influences the distribution of PS and PMMA block; meanwhile, block ratio has certain effect on the pore size. Effects of two different good solvents, dimethylacetamide (DMAC) and tetrahydrofuran (THF), on the membrane morphologies are also studied, the results exhibit that the block copolymer PS25-b-PMMA25 dissolved in both DMAC and THF could form channel pore, but the pore size is bigger for the DMAC system.