Organic montmorillonite

Liang, G., Xu, J., Bao, S., and Xu, W. 2004. Polyethylene/maleic anhydride grafted polyethylene/ organic-montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties. Journal of Applied Polymer Science 91 3974—3980. 

Kim, S.K., Kwen, H.D., Choi, S.H. Radiation-induced synthesis of vinyl eopolymer based nanocomposites filled with reactive organic montmorillonite clay. Radiat Phys. Chem. 81, 519-523 (2012)... 

Wang, J. Chen, Y Jin, Q., Organic Montmorillonite as a Substitute for Aero-silica in Addition-Type Liquid Silicone Rubber Systems. Macromol. Chem. Phys. 2005, 206, 2512-2520. 

Wong et al. [41] showed that sodium montmorillonite imparted a better thermal stability to polyvinylidene difluoride-polyethylene (PE) glycol polymers than did organic montmorillonite. They showed that ethyl-3-methylimidazolium tetrafluoro-borate-functionalized montmorillonite greatly enhanced the thermal stability of the polymer. Liu et al. [42] studied the effect of various organoclays on the heat stability of poly trimethylene terephthalate. 

A. D. Liu, T. X. Xie, and G. S. Yang, Comparison of polyamide-6 nanocomposites based on pristine and organic montmorillonite obtained via anionic ring-opening polymerization. Macromolecular Chemistry and Physics, 207 (2006), 1174-81. 

Xu, W.-B. Bao, S.-P. Shen, S.-J. Hang, G.-P. He, P.-S. Curing kinetics of epoxy resin-imidazole-organic montmorillonite nanocomposites determined by differential scanning calorimetry. 7. Appl. Polym. Sci. 2003, 88, 2932-2941. 

As mentioned in the Introduction, the further property improvement of PBT can be done by the PLS technique, especially by the polymer melt intercalation method. In this session, we discuss on the preparation and characterization of PBT/organic montmorillonite (MMT) (PBT/organoclay) nanocomposites using three kinds of organoclays, each possessing different ammonium cations, in order to see their effects on the morphology of the PBT hybrids. Table 9.2 shows the related structure information of three typical kinds of commercial organoclays produced by Southern Clay, Texas, USA (whose trade names are Cloisite 6A, Cloisite lOA and Cloisite 30B). 

Those preliminary studies were later extended to include the addition of organic montmorillonite nanoscale filler to the polysulfone/dicyanate mix-tures.i The major reason for the introduction of the filler is the significant improvement in properties that can be obtained at low clay contents. The exfoliated configuration for the clay is of particular interest because it maximizes the interactions, making the entire surface of the clay layers available for interactions with the polymer matrix. This should lead to dramatic changes in mechanical and physical properties. 

It is believed that clay minerals promote organic reactions via an acid catalysis [2a]. They are often activated by doping with transition metals to enrich the number of Lewis-acid sites by cationic exchange [4]. Alternative radical pathways have also been proposed [5] in agreement with the observation that clay-catalyzed Diels-Alder reactions are accelerated in the presence of radical sources [6], Montmorillonite K-10 doped with Fe(III) efficiently catalyzes the Diels-Alder reaction of cyclopentadiene (1) with methyl vinyl ketone at room temperature [7] (Table 4.1). In water the diastereoselectivity is higher than in organic media in the absence of clay the cycloaddition proceeds at a much slower rate. 

Methyltins are less likely than the butyl- and octyl-tins to partition to sediments, soils, and organic carbon. Modelled data for K c suggest much lower capacity for binding to organic carbon than do measured values, often by several orders of magnitude. Measured data have been used in preference to model environmental fate of the compounds. The compounds also bind strongly to clay minerals, montmorillonite in particular. 

Other studies use soil or sediment samples for a more accurate indication of microbial activity in natural environments. In these samples, organic matter and clay particles play a role in metal toxicity.76112113 Both organic material and clay particles in soil can bind metals and reduce their bioavailability. For example, Pardue et al.87 demonstrated that much less solution-phase cadmium was required to inhibit trichloroaniline (TCA) dechlorination in a mineral-based soil than in a soil containing a higher concentration of organic matter. Other studies have shown that adding clay minerals to a medium mitigates toxicity. Clay minerals, such as kaolinite, montmorillonite, bentonite, and vermiculite, can bind to metals to decrease the amount that is bioavailable.112 115... 

In a study of adsorption of organic herbicides by montmorillonite, Bailey and colleagues138 found that none of the compounds conformed to the Langmuir adsorption equation. Of the 23 compounds tested, only a few did not conform well to the Freundlich equation. 

As noted above, adsorption isotherms are largely derived empirically and give no information on the types of adsorption that may be involved. Scrivner and colleagues39 have developed an adsorption model for montmorillonite clay that can predict the exchange of binary and ternary ions in solution (two and three ions in the chemical system). This model would be more relevant for modeling the behavior of heavy metals that actively participate in ion-exchange reactions than for organics, in which physical adsorption is more important. 

The catalytic application of clays is related closely to their swelling properties. Appropriate swelling enables the reactant to enter the interlamellar region. The ion exchange is usually performed in aquatic media because the swelling of clays in organic solvents, and thus the expansion of the interlayer space, is limited and it makes it difficult for a bulky metal complex to penetrate between the layers. Nonaqueous intercalation of montmorillonite with a water-sensitive multinuclear manganese complex was achieved, however, with the use of nitromethane as solvent.139 The complex cation is intercalated parallel to the sheets. 

When organic cations (e.g., cationic tensides) are employed, clay organo-complexes are formed, which can be used in organic solvents. A Pd-hexadecy-lammonium montmorillonite catalyst was prepared by the reduction of Pd(OAc)2 by ethanol in the interlamellar space. At small ethanol concentrations in toluene, selective interlamellar sorption of ethanol was established consequently, the reduction also occurred only in the interlamellar space.160 The catalyst was used for the hydrogenation of alkenes.161... 

Fig. 6.20 Simplified diagram of montmorillonite clay with anionic and cationic organic compounds bonded to it (Ferris, 1998)...

The great importance of minerals in prebiotic chemical reactions is undisputed. Interactions between mineral surfaces and organic molecules, and their influence on self-organisation processes, have been the subject of much study. New results from Szostak and co-workers show that the formation of vesicles is not limited to one type of mineral, but can involve various types of surfaces. Different minerals were studied in order to find out how particle size, particle shape, composition and charge can influence vesicle formation. Thus, for example, montmorillonite (Na and K10), kaolinite, talc, aluminium silicates, quartz, perlite, pyrite, hydrotalcite and Teflon particles were studied. Vesicle formation was catalysed best by aluminium solicate, followed by hydrotalcite, kaolinite and talcum (Hanczyc et al., 2007). 

In this chapter, we demonstrate the potential of such agents as catalysts/promoters in key steps for the derivatization of sugars. The most significant catalytic approaches in carbohydrate chemistry that use aluminosilicate porous materials, namely zeolites and montmorillonite clays, are reviewed and discussed. Silica gel is a porous solid silicate that has also been used for heterogeneous catalysis of organic reactions in general. We include here its usefulness as promoter and reagent support for the reactions under consideration. 

A diverse group of organic reactions catalyzed by montmorillonite has been described and some reviews on this subject have been published.19 Examples of those transformations include addition reactions, such as Michael addition of thiols to y./bunsatu rated carbonyl compounds 20 electrophilic aromatic substitutions,19c nucleophilic substitution of alcohols,21 acetal synthesis196 22 and deprotection,23 cyclizations,19b c isomerizations, and rearrangements.196 24... 

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