Combined use of breath figures process and microphase separation of PS-b-P4VP to produce stable porous nanomaterials

Abstract

Among various templating strategies available for the preparation of porous polymer films, Breath Figures (BFs) as a fast, low-cost and versatile method has aroused extensive interest. However, the prerequisite of these porous polymer films for potential application is their stability in harsh environments. In this article, we report a new method to stabilise the porous materials prepared by BFs. Polystyrene-block-poly(4-vinylpyridine) block copolymer (PS-b-P4VP) is utilized to prepare well-organized honeycomb films with pore diameters ranging from 0.45 to 2 μm via BFs. Then ethanol is selected to swell the honeycomb porous membrane to generate a nanometer-sized microstructure by solvent induced microphase separation. After the microphase separation process by swelling in ethanol, pyridine moieties as hydrogen bond acceptor or alkaline catalyst are completely exposed, vitally important for the further improvement of film stability. On the one hand, monomers with hydrogen bond donors such as pyrrole, aniline, 3-thiopheneacetic acid can composite with the exposed pyridine groups by hydrogen bond interaction, and the subsequent chemical oxidation polymerization affords hierarchically porous conducting nanomaterials with thermal and solvent stability. On the other hand, the exposed pyridine groups can also be used as alkaline catalytic sites to hydrolyze inorganic precursor like TEOS on the skeleton of PS-b-P4VP for the final formation of silica inorganic porous films with prominently enhanced stability. All the results indicate that the combination of BF process and microphase separation is a versatile and effective method to produce various stable porous nanomaterials.