Application of thin films to porous mineral oxides using two‐dimensional solvents

Abstract

Thin polymeric films have been applied to the surface of a porous material in a novel process. Nitrogen sorption, a conventional tool for measuring surface areas and pore size distributions, can be employed for determining the thickness of such films through a comparison of the pore size distribution curves before and after film formation. The thickness of a polystyrene film on a porous alumina powder is determined and compared with the theoretical thickness for styrene polymerized inside a two-dimensional solvent, which consists of a partial bilayer of sodium dodecyl sulfate physically adsorbed from an aqueous solution onto the powder. Film thicknesses ranged from 1.8 to 0.4 nm while BET surface area decreased from 94.7 to 57.8 m2/g. The powder surface changes from hydrophilic to hydrophobic while retaining the basic pore structure.

Two-dimensional phase transition of styrene adsolubilized in cetyltrimethylammonium bromide admicelles on mica

“…Hence, additional adsolubilized solute coalesces inside the core, surrounded by an adsorbed layer of surfactant at the surface to reduce the surface energy. These styrene droplets serve as reaction sites that form polymer aggregates during admicelle polymerization [4].…”

“…Adsorbed aggregates (admicelles), whether discrete or continuous, possess some properties which are similar to those of micelles including the ability of adsolubilizing sparingly soluble/insoluble compounds in aqueous solutions [1]. Applications of adsolubilization include concentrating and removing selected organic constituents in environmental remediation [2], analyzing mixtures of optical isomers in admicellar chromatography [3], concentration of organic reactants in admicellar catalysis [4] and modification of surfaces by polymerization of monomers within admicelles, a process called admicellar polymerization [5][6][7].…”

“…The droplet sizes fall into two ranges, 100-200 nm and ≈20 nm. These droplets are thought to be responsible for the irregular patchy polymer film found after admicellar polymerization[4][5][6][7][18][19][20][21][22][23].…”

Synthesis, Structure and Reactivity of Disila‐ and Distanna ansa Half‐Sandwich Complexes of Molybdenum and Tungsten

“…The process has been used to modify the surface properties of various kinds of substrates, such as glass fibers,1 alumina,2–4 amorphous silica,5–8 titanium oxide,9 glass cloth,10 and nickel 11. Polymer thin films have been studied with various methods, including scanning electron microscopy,2, 3 ellipsometry,9, 10 Fourier transform infrared spectroscopy,3, 8 evaluation of the wearing properties of composites,3 scanning tunneling microscopy,11 and contact‐mode atomic force microscopy (AFM) 5, 11. These studies have not provided insights into any changes that may occur in the characteristics and morphology of polymer films because of changes in the admicellar polymerization process, specifically changes in the concentrations of the surfactant and monomer(s).…”

Atomic force microscopy characterization of ultrathin polystyrene films formed by admicellar polymerization on silica disks

“…Admicellar polymerization, or the polymerization of monomers solubilized in adsorbed surfactant aggregates, was first developed in the 1980s1–3 as a means of modifying the surfaces of various substrates. The process has been characterized as occurring in four steps: (1) surfactant adsorption/admicelle formation, (2) adsolubilization of monomer(s), (3) polymerization, and (4) surfactant removal.…”