Plane-Wave Density Functional Theoretic Study of Formation of Clay-Polymer Nanocomposite Materials by Self-Catalyzed in Situ Intercalative Polymerization

Abstract

It has recently been shown that the intercalation and subsequent in situ polymerization of organic monomers within the interlayer of clay minerals yields nanocomposites with novel material properties. We present results of plane-wave density functional theory (DFT) based investigations into the initial stages of the polymerization of methanal and ethylenediamine within the interlayer of sodium montmorillonite. Nucleophilic attack of the amine on the aldehyde is only observed when the aldehyde is protonated or coordinated to a metal ion. No evidence is found for the dissociation of water in the hydration sphere of the sodium counterions. The Brønsted acidity of the hydroxyl groups present in the silicate layers is significantly affected by their proximity to sites of isomorphic substitution. However, the most obvious Brønsted acid sources are shown to be unlikely to catalyze the reaction. Instead catalysis is shown to occur at the clay mineral lattice-edge where hydroxyl groups and exposed aluminum ions act as strong Brønsted and Lewis acid sites, respectively.

Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange

“…On the other hand, some researchers have disclosed that for clay swelling to occur, water molecules must pass from external regions (i.e., external surfaces, internal surfaces, and micropores) to the interlayer gallery, passing between all clay edges. It has been determined that, in contrast to the chemically-inert basal plane, the edges of particles are extremely reactive [6][7][8][9], containing both Brönsted acid and base groups. Other authors [9][10][11] have reported that the reactive nature of clay layer edges has been implicated in catalysis reactions, such as polymerization.…”

Solid Acid Catalysts: Modification of Acid Sites and Effect on Activity and Selectivity Tuning in Various Reactions

“…The other supports like MgO and Al 2 O 3 tend to decompose heteropolyacids [56][57][58][59]. Similar to heteropolyacids, montmorillonite clays also can be conveniently used as a solid acid catalyst in place of the conventional mineral acid reagents due to the presence of both Brønsted and Lewis acidities [60]. However, the applicability of montmorillonite clays for acid catalyzed organic transformations is restricted due to their low acidity.…”

Synthesis and characterization of ZnS-montmorillonite nanocomposites and their application for degrading eosin B

“…These MMT-based catalysts combined the functions of the nanoparticles and MMT together, and exhibited synergetic effects [24][25][26]. Several methods have been adopted to prepare MMT-based composites, among which surfactant or polymerassisted methods are often applied [27][28][29][30]. For example, Pd-MMT nanocomposites were prepared with the aid of surfactants, which showed high selectivity for the partial hydrogenation of 1-phenyl-1-pentyne to 1-phenyl-cis-1-pentene [17].…”