Synthesis of organized mesoporous metal oxide films templated by amphiphilic PVA–PMMA comb copolymer

Abstract

The morphology and structure of metal oxide films play pivotal roles in determining their properties in various applications, e.g., catalysis and energy conversion. We present a general synthesis of organized mesoporous metal oxide films with high porosity and good interconnectivity via a sol–gel process using an amphiphilic poly(vinyl alcohol)–poly(methyl methacrylate) (PVA–PMMA) comb copolymer as a structure-directing agent. PVA–PMMA synthesis proceeded via a one-step free radical polymerization, a scalable and economical method for polymer synthesis. Despite a very low combing degree (3 wt%), a large amount of PMMA (25 wt%) was combed to the PVA backbones, resulting in a unique microphase-separated structure. Using a mixed solvent (i.e., dimethyl sulfoxide/tetrahydrofuran) was critical in obtaining the micellization of PVA–PMMA and homogeneous metal oxide films. During the sol–gel process, the hydrolyzed metal precursor selectively interacted with the hydrophilic PVA backbones through coordination, leading to an organized mesoporous structure. Homogeneously well-organized mesoporous structures were obtained for TiO₂, SiO₂, Al₂O₃, and ZrO₂, but particulate structures were formed for Fe₂O₃ and ZnO owing to high reactivity and rapid hydrolysis. Detailed discussion of parameters determining morphology and structure is provided, which is essential for the rational design and reproducible construction of mesoporous metal oxides.