Smectite intercalation compounds with ethyl lauroyl arginate (LAE®): structure and thermal decomposition mechanisms evidenced by HT-FTIR and TG/FTIR

Abstract This study explores the structural and thermal behavior of different smectites intercalated with the cationic surfactant ethyl lauroyl arginate (LAE®) at loadings up to 1.0 of the smectites' cation exchange capacity (CEC). X-ray diffraction (XRD) confirmed systematic expansion of the basal spacing ( d 001 ), reaching up to 2.29 nm, with changes governed by surfactant content, exchangeable cation type, and layer charge. LAE® was incorporated exclusively via ion exchange, as evidenced by exchangeable cation release, although steric hindrance limited full CEC saturation at higher loadings. Fourier transform infrared spectroscopy (FTIR) showed that the smectite framework remained intact, while band shifts in the N–H, C=O, and CH 2 regions indicated strong surfactant–clay mineral interactions and LAE® conformational changes. Thermogravimetric analysis revealed a reduction in decomposition steps from six (pure LAE®) to four upon intercalation, alongside a shift in the main decomposition peak from 285.7°C to 305.1°C for sample based on the Arizona smectite having high layer charge. Evolved gas analysis (TG-FTIR) confirmed altered degradation pathways for the organosmectites, with the suppression of nitrogen-containing volatiles such as NH 3 and NO 2 . High-temperature FTIR (HT-FTIR) further demonstrated reduced molecular mobility and enhanced thermal stability, particularly in samples with the highest LAE® content. Quantitative spectral analysis showed persistent C–H, C=O, and C–N–H bands at elevated temperatures, confirming the stabilizing effect of interlayer confinement. These findings underscore the potential of LAE®-modified smectites as thermally robust, non-toxic hybrid materials with promising applications as feed additives. Graphical abstract