The behavior of a system of two-dimensional elongated particles (discorectangles) packed into a slit between two parallel walls was analyzed using a simulation approach. The packings were produced using the random sequential adsorption model with continuous positional and orientational degrees of freedom. The aspect ratio (length-to-width ratio, ε = l/d) of the particles was varied within the range ε ∈ [1; 32] while the distance between the walls was varied within the range h/d ∈ [1; 80]. The properties of the deposits when in the jammed state (the coverage, the order parameter, and the longrange (percolation) connectivity between particles) were studied numerically. The values of ε and h significantly affected the structure of the packings and the percolation connectivity. In particular, the observed nontrivial dependencies of the jamming coverage ϕ(ε) or ϕ(h) were explained by the interplay of the different geometrical factors related to confinement, particle orientation degrees of freedom and excluded volume effects.
The effects of acid activation of Laponite RD (Lap) on the structure and properties of activated Lap nanoparticles (aLap) and the properties of polyNIPAA m hydrogels physically cross-linked by aLap have been studied. The acid activation of Lap by the sulfuric acid was done using the concentration of sulfuric acid within the interval C a = 0.525−14.58% for 10 h. For slightly activated samples (C a ≤ 1.25 wt %), the significant increase of the specific surface area (by ≈1.56 times) was accompanied with a significant decrease in both the values of the specific heat of immersion in water and n-decane. However, the hydrophilic properties of all samples S 0 −S 5 were still observed. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) data, Fourier transform infrared (FTIR) spectra, and X-ray diffraction (XRD) patterns demonstrated that the acid activation resulted in the destruction of the crystal lattice of Lap, leaching of magnesium and lithium, and formation of the amorphous phases. Moreover, the acid activation significantly affected aggregation and negative surface charges of the aLap faces in aqueous suspension. The effects of aLap on the swelling properties and cooperativity in the phase transitions of polyNIPAA m hydrogels cross-linked by aLap are also discussed. It was demonstrated that an increase in C a resulted in a significant increase in the equilibrium degree of swelling of the hydrogels and a decrease in the hydrogel phase-transition temperature from the swollen phase to the shrunken phase.
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