Dimethylamino- and trimethylammonium-tipped oxyethylene–oxybutylene diblock copolymers and their use as structure-directing agents in the preparation of mesoporous silica

摘要: Oxyethylene–oxybutylene diblock copolymers with a dimethylamino tip to the hydrophilic block were prepared by anionic polymerization, using aminoalcohol initiators in dry aprotic medium. Conversion of high percentage alcohol alkoxide minimized formation unwanted by-products, but slightly broadened molar mass distribution copolymers. Trimethylammonium-tipped quaternization methyl iodide. The utilised as structure-directing agents preparation silica under acidic conditions, where all carry positive charge, and subsequent removal calcination gave mesoporous materials. mesostructure depended on relative sizes polymer blocks, changing from body-centred cubic three-dimensional hexagonal two-dimensional decreasing proportion units. overall dimensions, determined from X-ray analysis, increased an increase micelle size, mesopore determined nitrogen adsorption size core hydrophobic block. A simple model is suggested which chains are embedded walls uncalcined silica, generating micropores calcination, whilst form separate microphase, giving rise mesopores calcination. effect charged tips, compared equivalent nonionic copolymers, expand dimensions mesostructures obtained generate higher surface areas calcined products.