| Inspired by the channels in the cell membranes for water transportation, water transport channels were constructed in the synthetic membranes for gas dehumidification to facilitate the diffusion of water. Meanwhile, the thickness of the membrane was significantly reduced to decrease the diffusion path. Thus, the dehumidification performances could be improved. The goals of this dissertation were to design the the water channels rationally and fabricate composite membranes with ultra-thin skin layer. The water/propylene mixture was chosen as the model system. Four kinds of composite membranes, including PVA-EDTMPA/PS, PVA-silica/PS, Gelatin-silica/PS and polydopamine/PS, were fabricated. The as-prepared membranes were characterized by SEM, TEM, NMR, XRD, DSC, TG and PAS etc. And the sorption properties, diffusion properties and the separation performance were investigated extensively. Molecular dynamics simulation was employed to probe the microstructure and diffusion process of water molecules in the membranes.In the PVA-EDTMPA/PS composite membranes, the size and amount of the water channels were enhanced and the water states were adjusted by the stronger interaction between EDTMPA and PVA. At low EDTMPA content (<10 wt.%), the increase of water diffusion coefficient was mainly attributed to enlarged size and amount of water channels. At high EDTMPA content (10-30 wt.%), the increase of water diffusion coefficient mainly araised from the variation of water states. Diffusion coefficients of water increased with the increasing proportion of free water, since the mobility of free water was much higher than that of bound water. The water permeance of PVA-EDTMPA/PS membranes with the highest amount of free water (24 %) reached 997.7 GPU and the separation factor increased to infinity for water/propylene (0.3 wt.%) mixture, when the content of EDTMPA in the membranes was 20 wt.%.Composite membranes with ultrathin PVA-silica nanohybrid skin layer (0.8-1.0μm) were fabricated by a novel approach combing the biomimetic mineralization and polymer mediated method. The silica particles induced by protamine in confined space within the crosslinked PVA matrix showed a uniform size without aggregation. The silica nanoparticles with the average diameters 14.3, 9.5 and 8.0 nm were generated by controlling the size of confined space via adjusting the thermal treatment temperature. Since the diffusion coefficients of water in the interfacial water channels (2.82×10?7 cm2/s) was higher than that in the PVA bulk region (1.05×10?7 cm2/s), the water permeance of the composite membranes was increased to 1200 GPU, meanwhile, the separation factor increased to infinity for water/propylene (0.3wt.%) mixture (sodium silicate concentration 30 mM, pH 7.0, dipping time 1 h).Composite membranes with ultrathin Gelatin-silica nanohybrid skin layer (0.8-1.0μm) were fabricated based on biomineralization principle utilizing the inducing and membrane-forming properties of the gelatin. The size and morphology of the well-dispersion silica particles in the hybrid membranes can be controlled by the fabricated conditions. Since the existence of gelatin-silica interfacial water channels and the desirable connectivity of water channels in the gelatin bulk, the water permeance of the composite membranes was increased to 2497 GPU, meanwhile, the separation factor increased to infinity for water/propylene (0.3wt.%) mixture (silica content 4.5 wt.%, pH 7.0, fabricated temperature 40 oC).Inspired by the bioadhension principle, composite membranes with ultrathin defect-free skin layer (10-90 nm) were fabricated utilizing the self-polymerization of dopamine and its strong interaction with support layer. The thickness and compactness of the skin layer were conveniently tuned by varying fabrication conditions. The as-prepared membranes displayed special structure, which induced the continuous water channel. The water permeance of the composite membranes was 9316.7 GPU, and the separation factor of water vapor/propylene was infinite for water/propylene (0.3 wt.%) mixture (the dopamine concentration 2 mg/ml, pH 9.4, dipping time 0.5 h).
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