title: Towerlike SBA-15: base and (10)-specific coalescence of a silicate-encased hexagonal mesophase tailored by nonionic triblock copolymers.
abstract: Hydrothermal templating of mesoporous molecular sieves by nonionic triblock copolymers [poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) (PEO-PPO-PEO)] at specific block lengths of EO(20)PO(70)EO(20) and selected 2 M HCl dosage (pH -0.3) caused the formation of micrometer-sized SBA-15 hexagons with well-ordered hexagonal pore channels (pore size and wall thickness of approximately 6 nm and pore-to-pore distance of approximately 12 nm) after template removal. For a beneficial lower surface energy, these {10} laterally coalesced hexagons tend to stack imperfectly over the base into towerlike entities, leaving dislocations and faults within the single domain thus formed. Evidence for the mechanism of Brownian motion/coalescence of the hexagonal-mesophase particulates, previously suggested for MCM-41 accretion in the presence of cationic surfactant, is more clearly identifiable in the present low-pH case of amphiphilic block copolymer templates and linear silica oligomers.
authors.affiliation: Department of Chemical Engineering, Tung-Fang Institute of Technology, Hu-Nei, Kaohsiung 829, Taiwan.
authors.forename: Yauh-Yarng
authors.initials: YY
authors.lastname: Fahn
authors.forename: An-Chung
authors.initials: AC
authors.lastname: Su
authors.forename: Pouyan
authors.initials: P
authors.lastname: Shen