Pore-scale modelling and tomographic visualisation of drying in granular media

Spatio-temporal evolution of liquid phase clusters during drying of a granular medium (realised by random packing of cylindrical particles) has been investigated at the length-scale of individual pores. X-ray microtomography has been used to explicitly resolve the three-dimensional spatial distribution of the solid, liquid, and gas phases within the wet particle assemblies. The propagation of liquid menisci through the granular medium during drying was dynamically followed. The effect of contact angle on the degree of dispersion of the drying front has been studied by observing drying in a layer of untreated (hydrophilic) and silanised particles; the drying front was found to be sharper in the case of the silanised (less hydrophilic) particles. This observation was confirmed by direct numerical simulations of drying in a digitally encoded porous medium identical in structure to the experimental one. The simulations also revealed that the average gas-liquid interfacial area in a given porous microstructure strongly depends on the contact angle.     

In‐column preparation of a brush‐type chiral stationary phase using click chemistry and a silica monolith

Brush‐type chiral stationary phases (CSP) have been prepared both from a silica monolith and, separately, from 10 μm porous silica beads via a process of in‐column modification including attachment of the chiral selector via copper‐catalyzed azide–alkyne cycloaddition. Azide functionalities were first introduced on the pore surface of each type of support by reaction with 3‐(azidopropyl)trimethoxysilane, followed by immobilization of a proline‐derived chiral selector containing an alkyne moiety. This functionalization reaction was carried out in dimethylformamide (DMF) in the presence of catalytic amounts of copper (I) iodide. The separation performance of these triazole linked stationary phases was demonstrated in enantioseparations of four model analytes, which afforded separation factors as high as 11.4.     

Characterization of poly(methylphenylsilane) prepared by plasma polymerization

Poly(methylphenylsilane) plasma polymer layers of the thickness ranging from 10⁻² to 10⁰ μm intended to engineer interphases in glass fibre reinforced polymer composites and light-emitting displays were prepared by r.f. glow discharge technique. The films synthesized from a mixture of dichloro(methyl)phenylsilane vapor and gaseous hydrogen were deposited on flat glass and silicon substrates and glass fibres as well. Deposition conditions were optimized to obtain required thickness, mechanical and electrical properties of interphases. Prepared layers were amorphous, relatively rigid and transparent at room temperature with excellent adhesion to substrates. The surface of plasma polymer is rough with isolated (silicon substrate) and conglomerate (glass substrate) grains. FTIR and XPS spectra revealed a great amount of atomic oxygen bound to silicon atoms and enabled to determine the atomic concentrations. The structure model is proposed assuming a carbosiloxane network with not-crosslinked methyl and phenyl groups.     

Properties of epoxy systems with clay nanoparticles

Low molecular epoxy resin was mixed with different concentrations of montmorillonite clay with alkylamine-modified surface. The presence of the clay nanoparticles influences the gel time of the amine cured resin as well as the mechanical properties. Toughness and modulus, both in the glass and the rubberlike region, increase with clay concentration. An increasing amount of lower mobility phase with increased clay concentration was observed.