| High humidity induced process is an emerging method for preparing porous membranes with regular structure. Polymers were dissolved in volatile solvent and cast onto a substrate in a humid atmosphere, water droplets condensed onto the cool surface induced by the evaporation of the volatile solvent and arranged into a honeycomb pattern, at the same time, water droplets acted as the template around which the polymer assemble. After the solvent evaporated, a membrane with quite regular honeycomb pores was formed. To explore the route to control the structure of the membranes, it was aimed to reveal the mechanism of this process in this paper.In this paper, regular honeycomb membrane of sulfone polymers with micron-sized cells (1-5 μm) both on the membrane surface and inside the membrane were prepared by casting the polymer solution in chloroform in an atmophere with high humidity. The pore sizes on the membrane surface were quite uniform. Pores in different size could be obtained by changing the humidity, the concentration of the solution and the molecular weight of the polymer. The pore size increased with the humidity. As the concentration of the cast solution increased, the pore size of the film decreased and tended to change from circular into hexagon in shape. In the same weight concentration, the pore size increased with the molecular weight. In addition, the film pattern was greatly influenced by the volatility, the miscibility between solvent and water, the flow rate of humid air, etc. With regard to the formation mechanism of honeycomb pattern both in the surface and the interior of membrane, the formation process of water template could be described with four steps: "isolated water droples"-"coexistence of isolated water droplets and islands"-"big blocks"-"big blocks be pushed into integrated membrane". Cultured on this film, the rat hepatocytes were found to be alive, which indicated the good biocompability of this film. The honeycomb membrane with regular pore size represented a high contact angle up to 124.6°, while the contact angle of polysulfone wasabout 82°, the hydrophobicity was increased. The membrane formed on a steel meshwork with high humid induced method had a pore diameter of about 0.5~ 1μm and almost all the pores were through.While preparing honeycomb membranes with the chloroform solution of Udel 3500 PSF and Udel 1700 PSF, an interesting phenomenon was found that Udel 3500 PSF could form a quite regular honeycomb pattern, while Udel 1700 PSF could only form a transpant membrane without any pattern. In addition, chloroform solution of PGA-PLA, PPESK could also form honeycomb pattern while polycarbonate could not. It was supposed that whether one kind of polymer can form a honeycomb pattern or not was determined by its adsorption behavior on the interface of solvent and water. And the adsorption is relative to the interface tension of solvent and water. The adsorption is positive as the interface tension increases with the solution concentration, while the adsorption is zero or negative as the interface tension doesn't change or decreases with the solution concentration. Only when the adsorption is positive, the formation of a stable interface is possible. And the interface film will enwrap the water droplets to form an obstruct preventing the coalescence of them. The results of interface tension mesurement between polymer solution in chloroform and water indicated that PGA-PLA, Udel 3500 PSF, PPSEK, and PSF with a carboxyl side group possessed a positive adsorption while PC and Udel 1700 PSF possessed a negative adsorption and a zero adsorption, which accorded well with the supposition above. Furthermore, through the analysis of the adsorption quantity and the phenomenon that Udel 3500 PSF solution in chloroform stored for 30 days could prepare a more regular honeycomb pattern, it was supposed that the compactness and intensity of interface film was another determinant parameter of highly regular honeycomb pattern.A membrane with regular honeycomb pattern not only on the surface but inside the membrane was prepared with the chloroform solution of PSF. The movement of water droplets with Marangoni effect and the Gibbs free energe of system were combined tointerpretate the multiple layers of honeycomb pores. The water droplets were regulated into small islands by the inter-attractive and repulsive force, and then arranged into large blocks with the Marangoni effect. According to the calculation of the Gibbs free energe of the system, the Gibbs free energy exhibited a minimum value when the droplets were inside the solution as the solvent was chloroform. When carbon disulfide was used as the solvent, with the increase of solution concentration, the doplet position with minimum Gibbs free energy varied from surface to interior. So the chloroform solution can obtain a multiple layer honeycomb membrane, while the carbon disulfide solution can obtain either single layer or multiple layer honeycomb pattern according to the concentration of the solution.In addition, a study of the hodrophobic modificaiton of polyethersulfone microporous membrane to be used in membrane distillation was also carried out. The surface of the polyethersulfone membrane was modified with perfluohexane by plasma polymerization. The contact angle of water reached 120°. The modified membrane was used in vacuum membrane distillation (VMD). VMD measurements revealed that this modified polyethersulfone membrane had a desalination rate of 99.99% and a distillation flux of 4530ml/m~2·h for 3.5% Nacl solution.
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