DMSO Intercalation in Selected Kaolinites: Influence of the Crystallinity

Spectral and conductivity measurements insights on loading mechanisms of DMSO/water-kaolin complexes

Kaolin, a naturally occurring clay mineral renowned for its distinctive properties, holds significant importance across various industries. The integration of dimethyl sulfoxide (DMSO) into kaolin matrices, both in the presence and absence of water, has been extensively explored for its potential to enhance material characteristics. Addressing debates surrounding the proposed adsorption mechanism for the type I structure of DMSO, this study undertook a comprehensive physicochemical characterization of DMSO-kaolin complexes (DMSO-KCs) derived from untreated (UnK) and HCl-treated (HK) Egyptian ore, with a focus on elucidating the loading mechanism facilitated by water. Key insights gleaned from electrical conductivity, dielectric constant, and Fine Testing Technology - Fourier-transform infrared (FTT-FTIR) measurements, shedding light on the bonding nature of DMSO-KCs. FTT-FTIR analysis revealed two stages of water departure at 180 °C, with the final stage coinciding with the release of pyrolysis gases, confirming the catalytic degradation of DMSO. Through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), two distinct bonding types of DMSO molecules with kaolinite were identified: amorphous adsorbed (type I) and lattice-oriented intercalated (type II). Electrical characteristic evaluations within the temperature range of room temperature (RT) to 260 °C and frequency range of 42 Hz-1 MHz revealed that DMSO intercalation enhances the electrical properties of kaolin. Hydrated DMSO-KCs exhibited higher values of σac and ɛ' compared to non-hydrated samples. The activation energy (Ea) values for HCl-treated samples were smaller than those of untreated ones. Alternating current (AC) conductivity analysis indicated predominantly ionic behavior with frequency and temperature dependency in both HCl-treated and untreated kaolin. Our findings substantiate the adsorption mechanism of Type I DMSO, highlighting its amorphous nature, instability, and catalytic degradation over time, in contrast to the intercalated type II. This elucidation is pivotal for understanding the behavior of DMSO-KCs across diverse applications, including electronics, ceramics, and materialsscience.

The Stability and Properties of Polystyrene/Kaolinite Nanocomposites during Synthesis via Emulsion Polymerization

The aim of this work was to study the stability and morphological properties of polystyrene latex containing kaolinite as a filler during the process of synthesis of nanocomposites viaemulsion polymerization. Nanocomposites with 1, 3, and 5 wt% of kaolinite were prepared. Latexes with 1 to 3 wt% of kaolinite were stable during the polymerization reaction. Hydrodynamic diameters of 93.68 and 82.11 nm were found for latexes with 1 and 3 wt% of kaolinite, respectively. The quantities of 1 to 3 wt% of kaolinite added during the reaction did not influence the reaction conversion curves or the number of particles. X-ray diffraction (XRD) and unconventional techniques of scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) showed the presence of exfoliated and intercalated structures of the kaolinite.

DMSO Deintercalation in Kaolinite–DMSO Intercalate: Influence of Solution Polarity on Removal

This study focused on the deintercalation of dimethyl sulfoxide (DMSO) from a kaolinite–DMSO complex in various solvents. The use of kaolinite as filler in polymer–clay composite generally faced the difficulty of kaolinite dispersion due to its high cohesion. For improved dispersion of kaolinite within a given matrix, previous intercalation of small polar molecules is usually done prior to its displacement during composite-making. The influence of the solvent polarity on the deintercalation in analyzed here to understand its role during the deintercalation process. The intercalation of the DMSO was done by solution-mixing and its displacement was done in distilled water, ethyl acetate, and acetone. The products of deintercalation were analyzed using Fourier transform infra-red (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The weakening of the kaolinite cohesion after DMSO intercalation is demonstrated through the broadening of the diffraction peak associated with the kaolinite on XRD patterns. From FTIR spectra, the weakening is associated with the displacement to low wavenumbers of the Si–O or Al–O vibration bands within the kaolinite–DMSO complex. The kaolinite dehydroxylation temperatures from DSC show that the rate of DMSO displacement affects the ordering of the recovered kaolinite. The crystallite size of the kaolinite is reduced from the raw to the recovered kaolinite after DMSO displacement, indicating an exfoliation of the kaolinite. From these results, it is found that the removal of the DMSO from the kaolinite–DMSO complex is influenced by solvent polarity. The higher the polarity, the greater the removal of the DMSO from the complex. Solvent polarity affects the rate of DMSO displacement, which influences the ordering of the recovered kaolinite. It is suggested that solvent polarity can be used to control the removal rate of DMSO, which may be key to the dispersion of the kaolinite platelets.