Fabrication Of Porous Thin Films Through Selective Photo-Cross-Linking Strategy

Compared with the thin films with smooth surface, the porous thin films have higher specific surface area. The porous structure has a strong adsorption effect for macromolecules and nanoparticles. The various porous films have selective permeation effect on different molecules. So, the research for fabrication of porous thin film is significant to separation membrane, bioengineering, drug release and sensors. In this thesis, we discussed a method for fabrication of composite thin film. A kind of porous film was obtained by selective photo-cross-linking.First, we used two kinds of polyelectrolytes (PAH and PEI) with positive charge and a negatively charged polyelectrolyte (PSS) as building blocks to adsorb on the substrate through the electrostatic interaction. Then multilayer films were cross-linked by a photosensitive chemical cross-linking agent (DAS). DAS cross-link selectively two polyelectrolytes (PAH and PSS) under UV excitation condition, leading to the formation of stable covalent bond. However, another polyelectrolyte (PEI) cannot be cross-linked. The proportion of the films with different stability was formed. Finally, we soaked the cross-linked multilayer films in alkaline aqueous solution. The alkaline environment will damage the interaction of non-cross-linking polyelectrolyte to fall off from the multilayers films with the formation of defection, and the cross-linked polyelectrolytes remained relatively stable in alkaline solution. The porous structure was formed through the process. Then we researched the permeability and surface topography of the porous films...