title: Analysis of microporosity in ordered mesoporous hierarchically structured silica by combining physisorption with in situ small-angle scattering (SAXS and SANS).
abstract: The combination of physisorption experiments with simultaneous in situ small-angle X-ray and neutron scattering (SAXS/SANS) was used to elucidate the porosity in mesoporous silica with a trimodal pore structure. The material ("KLE-IL") contains spherical mesopores of 14 nm in diameter, worm-like mesopores (2-3 nm), and micropores, templated by a block copolymer and an ionic liquid surfactant, while the micropores originate from the hydrophilic block of the block copolymer. The main objective of the study was the quantification of the microporosity and the small mesopores and to find out if they are indeed located between the larger, spherical mesopores. Our in situ SAXS/SANS experiments took advantage of contrast matching of nitrogen (SANS, T = 77 K) and dibromomethane (SAXS, T = 290 K). By using the latter gas with a slightly larger kinetic diameter, it was possible to judge the accessibility of the pores under ambient conditions. The in situ experiments were supported by high-precision ex situ physisorption. Using suitable approaches for the SAXS/SANS analysis, it was possible to separate the content of the micropores and small mesopores.
authors.affiliation: Institute of Physical Chemistry, University of Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Mascotto
authors.forename: Dirk
authors.initials: D
authors.lastname: Wallacher
authors.forename: Astrid
authors.initials: A
authors.lastname: Brandt
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauss
authors.forename: Matthias
authors.initials: M
authors.lastname: Thommes
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Zickler
authors.forename: Sérgio S
authors.initials: SS
authors.lastname: Funari
authors.forename: Andreas
authors.initials: A
authors.lastname: Timmann
authors.forename: Bernd M
authors.initials: BM
authors.lastname: Smarsly
mesh_terms: D012542:Scattering, Radiation; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide