Polymer-inorganic hybrid membranes morphology

Recent developments in material science have produced a wide variety of options for the organic and the inorganic phase in the synthesis of advanced hybrid membranes. However, the achievement of proper mixed matrix morphology can be very challenging, and the choice of the polymer and the inorganic flUer should be made according to their chemical characteristics. 

The choice of the polymer and fillers is very important to develop advanced hybrid membranes for a particular separation process, but the major challenge is to prepare a defect-free interface between the organic and inorganic phase. Indeed, the interfacial morphology plays a crucial role for the determination of the transport properties of the hybrid matrix, and a departure from ideal conditions can lead to a severe worsening of the separation performance. In Fig. 7.6 the possible conditions at the interface are shown. 

The sol-gel process performed in low concentrated polymer-solvent solutions is another attractive route to develop hybrid membranes because it allows an in situ dispersion of metal-based nanoparticles within the polymeric matrix, achieving a suitable interfacial morphology between the continuous and the dispersed phase. Silica particles and polyimide have been frequently used to produce these hybrid membranes [107,108]. In general, hydrolysis and condensation reactions are involved in the sol-gel process, when alkoxides are involved in the formation of the dispersed phase. The advantage of using this method is the formation of an inorganic network largely interconnected with the polymeric materials mainly with noncovalent interactions [109]. In Fig. 7.10 a... 

Figure 7.6 Different cases of interfaciai morphology in hybrid organic-inorganic membranes. Adapted from T.-S. Chung, L.Y. Jiang, Y. Li, S. Kulprathipanja, Mixed mabix membranes (MMMs) comprising organic polymers with dispersed inorganic flUers for gas separation. Progress in Polymer Science 32 (2007) 483-507.

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