Self-Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores

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Abstract

We report the self-assembly and characterization of mesoporous silica thin films with a 3D ordered arrangement of isolated spherical pores. The preparation method was based on solvent-evaporation induced self-assembly (EISA), with MTES (CH3–Si(OCH2CH3)3) as the silica precursor and a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer as the structure-directing agent. The synthetic approach was designed to suppress the siloxane condensation rate of the siloxane network, allowing co-self-assembly of the silica and the amphiphile, followed by retraction of the PEO chains from the silica matrix and matrix consolidation, to occur unimpeded. The calcined films retained the methyl ligands and exhibited no measurable microporosity, thereby indicating that the 3D-ordered spherical mesopores are not interconnected. A solvent-mediated formation mechanism is proposed for the absence of microporosity. Due to their closed porosity and hydrophobicity, the MTES-based films and MTES-TEOS (Si(OCH2CH3)4)-based hybrid films we describe should be promising for applications such as low-k dielectrics.

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