Phase Transitions in Complexes of Nontronite with <i>n</i>-Alkanols

Pfirrmann, G.

doi:10.1346/ccmn.1973.0210406

Cited by 18 publications

(8 citation statements)

References 6 publications

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“…Temperature Dependence of Morphology in Organoclays. Lagaly et al , investigated the complexes formed by montmorillonite-like bedellite and nontronite clays with n -tetradecylammonium and n -alkanols containing 8−22 CH 2 groups. On the basis of the X-ray diffraction (XRD) data, they suggested that these compounds underwent a phase transition at high temperatures resulting in a steplike decrease in the basal spacing d L .…”

Section: Background On Organoclaysmentioning

confidence: 99%

Thermally Induced Phase Transitions and Morphological Changes in Organoclays

et al. 2004

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Thermal transitions and morphological changes in Cloisite organoclays were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and in situ simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) over the temperature range of 30-260 degrees C. On the basis of DSC and FTIR results, the surfactant component in organoclays was found to undergo a melting-like order-disorder transition between 35 and 50 degrees C. The transition temperatures of the DSC peaks (Ttr) in the organoclays varied slightly with the surfactant content; however, they were significantly lower than the melting temperature of the free surfactant (dimethyldihydrotallowammonium chloride; Tm = 70 degrees C). FTIR results indicated that within the vicinity of Ttr, the gauche content increased significantly in the conformation of surfactant molecules, while WAXD results did not show any change in three-dimensional ordering. Multiple scattering peaks were observed in SAXS profiles. In the SAXS data acquired below Ttr, the second scattering peak was found to occur at an angle lower than twice that of the first peak position (i.e., nonequidistant scattering maxima). In the data acquired above Ttr, the second peak was found to shift toward the equidistant position (the most drastic shift was seen in the system with the highest surfactant content). Using a novel SAXS modeling technique, we suggest that the appearance of nonequidistant SAXS maxima could result from a bimodal layer thickness distribution of the organic layers in organoclays. The occurrence of the equidistant scattering profile above Ttr could be explained by the conversion of the bimodal distribution to the unimodal distribution, indicating a redistribution of the surfactant that is nonbounded to the clay surface. At temperatures above 190 degrees C, the scattering maxima gradually broadened and became nonequidistant again but having the second peak shifted toward a scattering angle higher than twice the first peak position. The changes in SAXS patterns above 190 degrees C could be attributed to the collapse of organic layers due to desorption and/or degradation of surfactant component, which was supported by the TGA data.

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Section: Background On Organoclaysmentioning

confidence: 99%

Thermally Induced Phase Transitions and Morphological Changes in Organoclays

et al. 2004

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“…The structure of kaolinite intercalates is now established by several X-ray diffraction studies (DMSO, NMFA, imidazole, pyridine-N-oxide, picoline-N-oxide, Weiss et al 1966;Weiss & Orth 1973> Weiss et al 1973)* The first three-dimensional crystal structure analysis was made of a NMFA-dickite complex (Adams 1978 a ) .A neutron powder diffract into the hydrogen bonding scheme in the formamide-kaolinite complex (Adams et al 1976).…”

Section: Structure Of Kaolinite Intercalatesmentioning

confidence: 99%

Clay-organic interactions

Lagaly

1984

Phil. Trans. R. Soc. Lond. A

205

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Clay minerals interact with organic materials by adsorption, intercalation and cation exchange. Basic principles of intercalation reactions were obtained with kaolinite which intercalates a limited number of neutral organic compounds. The interaction of neutral organic compounds with mica-type layer silicates (2/1 clay minerals) is of quite different type. As illustrated for the interaction with nuclein bases, the adsorption can be strikingly dependent on the layer charge and the concentration of salts and co-adsorption phenomena can occur. Various organic materials are bound by cation exchange. Besides some other examples, the reaction with alkylammonium ions is of interest because of widespread practical applications. From a more scientific point of view, the interactions of alkylammonium ions with clays provide models for studying surfactant aggregations on solid surfaces and possible conformational changes in aggregates of long chain compounds (mono- and bimolecular films, as in biomembranes). Negatively charged organic ions can also be bound by clays. The main mechanisms are binding by positive edge charges or exchanging structural OH-groups.

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“…Later on, several papers dealt with these compounds: orientation of alkanol molecules (MacEwan, 1948), influence of inorganic (Dowdy and Mortland, 1967;Bissada et al, 1967) and organic (Weiss, 1963) interlayer cations and of charge density (Lagaly and Weiss, 1967) onto the alkanol orientation, selectivities for distinct alkanols from mixtures (Heydemann and Brindley, 1968;Slabaugh and Hanson, 1969;Aragon de la Cruz, 1969) and temperature dependent phase transitions with inorganic interlayer cations (Brindley and Ray, 1964;Pfirrmann et al, 1973).…”

Section: Introductionmentioning

confidence: 99%