Promoted and Controllable Self-Assembly of Hydrolyzed Siloxane and Triblock Copolymer under Organic Polyhydroxy Acids

Abstract

Large-molecule polyhydroxy organic acids such as tartaric acid and citric acid were found to significantly promote the cooperative formation of mesoporous silica SBA-15 with homogeneous well-defined hexagonal mesostructure under much weaker acidities without addition of volatile inorganic acids; therefore a novel environmental benign route for SBA-15 synthesis was developed. It is suggested that the polar groups of polyhydroxy acid molecules can greatly strengthen the assembly interactions between the silica species and the triblock copolymer by providing hydrogen bonding. More interestingly, by controlling the strength of hydrogen-bonding interaction that is dependent on the concentration of carboxylic acids, the particle size of the product can be tailored. The silica with small particle size synthesized with a small amount of polyhydroxy acids was favorable support of palladium catalyst for the complete oxidation of volatile organic compounds in atmosphere, probably due to the facilitated diffusion of reactant molecules.

Mesoporous Silica-Supported Manganese Oxides for Complete Oxidation of Volatile Organic Compounds: Influence of Mesostructure, Redox Properties, and Hydrocarbon Dimension

“…Furthermore, comparing the images of the OMSs and of the commercial silicas, it is found that the aggregates of OMSs are significantly thicker than those of the commercial silicas. During the self-assembly synthesis of OMSs, the supermolecular organic templates generally exist in long-range-ordered stacking, and their strong interactions with silica oligomers induce silica accumulation and promote polymerization, leading to the formation of big aggregates. , …”

“…During the self-assembly synthesis of OMSs, the supermolecular organic templates generally exist in long- range-ordered stacking, and their strong interactions with silica oligomers induce silica accumulation and promote polymerization, leading to the formation of big aggregates. 32,33 The nitrogen sorption isotherms and the deduced BJH pore size distributions of the silicas are shown in Figure S2. Each isotherm shows an apparent increase of nitrogen uptake at relative pressures above 0.25, which corresponds to nitrogen capillary condensation taking place in the mesopores; the hysteresis loop on the nitrogen adsorption−desorption isotherm is also characteristic of mesoporous materials.…”