Computer Simulation On Preparation Of Polymer Porous Membrane By Non-solvent Induced Phase Separation

Porous polymer membrane plays an important role in chemical engineering separation.In recent years,non-solvent induced phase separation?NIPS?method has become a major approach in the preparation of porous polymer membranes;however,the mechanism of membrane formation is still unclear;the mechanism of membrane formation by double hydrophobic block copolymers is rarely studied.Besides,there is a key issue for the preparation of porous polymer membranes by the NIPS method,i.e.,the choice of good solvents.Most of good solvents are toxic and volatile;therefore,using green solvents during the NIPS process has attracted much attention.No researchers have explored the possibility and influence factors.Meanwhile,the modification of porous membranes with functional groups is also one of the directions of porous membrane modification in the future.In this thesis,the before-mentioned issues are investigated by dissipative particle dynamics?DPD?simulations.In the first part of the thesis,the membrane formation process of dual-hydrophobic PS-b-PMMA composed of polystyrene?PS?and polymethyl methacrylate?PMMA?is simulated by the NIPS method.It is found that polymer concentration is the main factor affecting the final morphology,the mesoporous membrane could be formed at the concentration range between25%-40%.Under different block ratios,the relative difference of the hydrophobicity of two polymers will make pore sizes different.In addition,different good solvents will lead to differences in micro-phase separation due to the different degrees of thermodynamic instability during evaporation,which will also affect the pore size of the porous polymer membrane.In the second part of the thesis,the possibility of preparing porous membranes by using the green solvent with the NIPS method is explored;the factors that affect the formation of membranes are investigated by simulating the process of preparing porous PVC membranes in the green solvent methyl 5-?dimethylamino?-2-methyl-5-oxopentanoate?Polar Clean?.It is found that PVC forms an uneven porous membrane at high concentrations.Grafting polyethylene glycol methacrylate?PEGMA?can improve its anti-fouling properties to a certain extent.PEGMA will form a hydration layer on the pore wall of the porous membrane.For the anti-fouling property of the membrane,if the grafting length of PEGMA is too long,irregular pores will be formed due to its over-strong hydrophilic effect.PVC grafted with PVC₄₀-g-PEGMA₅ has the best performance.In addition,increasing the ratio of PVC₄₀-g-PEGMA₅:PVC within a certain range can adjust the relative hydrophilicity of membranes,the distribution of water could be altered during micro-phase separation;thus,the pore diameter and the most efficient ratio for the largest pore of the porous membrane could be effectively increased,and the ineffective ratio would be reduced.The mechanical strength of the membrane is ensured when the permeability is increased.In addition,choosing an appropriate evaporation rate has a better effect on improving the effective ratio of porous membranes.In the third part of the thesis,the process of preparing the porous membrane modified Janus particles by using the solvent absorption and release method?SARM?with PS and PMMA blends is studied.During the process,it is found that over-low concentrations lead to dispersed Janus particles;the appropriate low concentrations lead to full Janus particles.Further increasing the concentration will lead to a stalactite-like structure.