Immersion Microcalorimetry and13C CP/MAS NMR Study of the Structure of Organoclays

Molecular Simulation of the Interlayer Structure and the Mobility of Alkyl Chains in HDTMA+/Montmorillonite Hybrids

“…This is in accordance with the suggestion deduced from FTIR and NMR spectra. [13][14][15][34][35][36][37] The decrease of the alkyl chain mobility with the increase of the intercalated surfactant cations is due to the decreasing distance between the alkyl chains that increases the dipolar interactions. 37 However, in the case of the same basal spacing, the same lateralmonolayer arrangement, and different surfactant number, the mobility of the atoms in the alkyl chains is constant.…”

“…Generally, as the interlayer packing density or the chain length decreases or the temperature increases, the intercalated chains adopt a liquidlike structure, i.e., the mobility of the chains increases. The following various experimental studies, including FTIR, 34-36 13 C MAS NMR, 14,15,37 and Raman spectroscopy, 38 provided more detailed and/or complementary information about the mobility of the alkyl chains. Li and Ishida 34 proposed that the tails of alkyl chains have higher mobility than the headgroups when the alkyl chains radiate from the clay surface with increase of the packing density.…”

Arrangement, conformation, and mobility of surfactant molecules intercalated in montmorillonite prepared at different pillaring reagent concentrations as studied by solid-state NMR spectroscopy

“…For example, 2 H, 1 H, and 13 C NMR have been used to study the dynamics of dimethyldistearylammonium montmorillonite [17] and n-octylammonium saponite [18]. With 13 C NMR relaxation time measurement and two-dimensional wide-line separation NMR spectroscopy (2D WISE), Wang et al investigated the structure and dynamics of hexadecyltrimethylammonium cations (HDTMA + ) in mesophase silicate [19] as well as the conformation heterogeneity and mobility of 1-octadecylamine intercalated in montmorillonite [20].…”

Changes in the morphology of organoclays with HDTMA+ surfactant loading

“…Accordingly, various models for the surfactant structural arrangements have been proposed chiefly based on XRD results. Recently, new approaches to the study of the surfactant structural arrangements including Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, Differential Scanning Calorimetry (DSC) and Magic-Angle-Spinning Nuclear-Magic-Resonance (MAS NMR) have been introduced to study the microstructure of organoclays and provided detailed conformational information [12][13][14][15][16][17][18][19][20]. However, these studies could not provide information about morphology and homogeneity of the organoclays.…”