Intercalation from solution

Intercalation from solutions in nonaqueous solvents (S21). This method may suffer from the drawback that final stoichiometries may not correspond to equilibrium conditions, because of partial leaching out of metal halide. For this reason, some chlorides can be intercalated only from solvents in which they have limited solubility iLS). It has often been the practice to wash intercalates with solvents to remove the excess of intercalant this may lead to stoichiometries lower than the original ones. The two-ampoule method may, therefore, be preferable (H24). 

Instead of relying on the volatility of the halide, as in the direct combination and two-bulb approaches, the solubility of halides may be exploited to intercalate from solutions of nonaqueous solvents . Although this technique allows reaction at relatively low temperatures, for which in situ monitoring of reaction progress is easy, the solvent may participate in the reaction through both co-intercalation and direct chemical reaction. 

The adsorption of neutral molecules on smectites is driven by various chemical interactions hydrogen bonds, ion-dipole interactions, coordination bonds, acid-base reactions, charge transfer, and van der Waals forces. Several polar molecules, such as alcohols, amines, and acids, form intercalation complexes with montmorillonites. The intercalation can be performed from the vapor, liquid, or even solid state. In intercalation from solution, solvent molecules are generally coadsorbed in the interlayer space. Guest molecules may be intercalated in dried clay minerals or may displace the water molecules of hydrated montmorillonite. 

Even though this technique has been mostly used with water-soluble polymers, such as PEO, polyvinyl ether (PVE), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA) [134-141], intercalation from nonaqueous solutions has also been reported [142-145]. For example, high-density polyethylene (HDPE)-based nanocomposites have been prepared by dissolving HDPE in a mixture of xylene and benzonitrile with dispersed organomodified layered silicates (OMLSs). The nanocomposite was then recovered by precipitation from tetrahydrofuran (THE) [143], Polystyrene (PS)/OMLS-exfoliated nanocomposites have also been prepared by the solution intercalation technique, by mixing pure PS and organophilic clay with adsorbed cetyl pyrid-ium chloride [146]. Similarly, several studies have focused on the preparation of polylactide (PLA)-layered silicate nanocomposites using intercalation from solution. 

William et al. (2005) reviewed various techniques for characterization and trends in the field of nanocomposites. These are new materials made with fillers, which have nanosize and have a big potential for applications in the automotive and aerospace industiy as well as in construction, electrical applications and food packing. There is a tremendous interest for using bio-nanoparticles in the new era of biocomposites by using synthetic and natural fillers in polymer nanocomposites. Aranda et al. (1998) studied the microwave-assisted blending-intercalation of ion-conductor polymers into layered silicates. They prepared organo-inorganic hybrid nanocomposites derived from poly(ethylene oxide) and montmorillonite silicate. They observed that ionic conductivity was enhanced as compared to samples prepared by intercalation from solution. 

Melt intercalationRecently, the melt intercalation technique has become the standard for the preparation of polymer/layered silicate nanocomposites and is also quite compatible with the recent industrial techniques. During polymer intercalation from solution, a relatively large... 

Silanol-terminated PDMS and hexadecyltrimethylammonium-exchanged clay were used to prepare PDMS-clay nanocomposites via melt intercalation [90]. The melt intercalation nanocomposites did not achieve as high a reinforcement as the aerosilica silicone hybrid, but the nanocomposite formed from solution had a nearly identical reinforcing effect on tensile strength as the aerosilica composite. 

First-stage intercalation conpoimds of FeCla were prepared and characterized by a variety of techniques (5.33). Two distinct preparation procedures were used (see scheme/ from vapour, using the established "two-bulb" method and from solution ising U.V. li t (see Experimental). 

Intercalation compounds of lithium and other species into the layered structure of graphite, synthesized by chemical methods, have been known for a long time. In the mid-1980s, the possibility of a reversible lithium intercalation from apro-tic solutions containing lithium salts into certain carbonaceous materials was discovered ... 

Reactions (5.5.30) and (5.5.31) proceed prevailingly during intercalation from solid or polymer electrolytes (cf. Section 2.6) or melts. When using common liquid electrolyte solutions, a co-insertion of solvent molecules (and/or intercalation of solvated ions) very often occurs. The usual products of electrochemical intercalation are therefore ternary compounds of a general composition ... 

In the case of solutions based on a solvent such as propylene carbonate (PC), the failure of graphite electrodes is attributed by some researches to the exfoliation of the graphite particles due to cointercalation of PC molecules with the Li ions.14,22 The difference between ethylene carbonate (EC) and PC in this respect may, according to this approach, be attributed to the higher ability of PC molecules to solvate Li ions.23 Hence, cointercalation of PC molecules takes place because their desolvation from Li ions, which migrate from solution phase to the intercalation sites in the graphite,... 

LDHs are also promising materials as sorbents for anionic organic contaminants via both ion-exchange and reconstruction reactions. There have been a large number of reports of the use of LDHs for removal of species such as aromatic carboxylic acids, phenols, pesticides, and humic or fulvic acids. Recently, Cardoso et al. [152] found that the sorption process of terephthalate anions from aqueous solutions by calcined Mg/Al - CO3 LDHs takes place by reconstruction of the LDHs and involves the intercalation and adsorption of terephthalate anions. Calcined Mg/Al - CO3 LDHs were found to be capable of removing 40 to 85 % of the benzoate from solutions in the concentration... 

The HSs and other aquatic and soil organic compounds interact with other components of the environmental system. Various kinds of clay organic intercalation compounds have been described, which are able to initiate unique photochemical reactivities characteristic of their specific molecular arrangements these differ considerably from solution photochemistry [18]. 

Intercalation of poly(ethylene oxide) into a lithium-ion exchanged clay gives an interesting class of layered silicate nanocomposites that are lithium-ion electrolytes. Componnds have been prepared by intercalation from methanol/water solutions and by melt intercalation. Melt intercalation typically gives samples with higher polymer contents than the solution method and with higher lithium-ion conductivity though the conductivity is probably stiU too low for practical applications. 

The acid phosphates, as the name suggests, also show acid-base intercalation reactions. For example, ammonia is intercalated from very dilute aqueous solutions to form... 

Composite electrodes made of two carbon components were evaluated experimentally as anodes for Li-ion batteries. The electrochemical activity of these electrodes in the reaction of reversible lithium intercalation from/to a solution of LiPFe in ethyl carbonate and diethyl carbonate was studied. Compositions of the electrode material promising for the usage in Li-ion batteries were found. 

Table IV compares for a series of dienes the yields of 1,2 addition products obtained with Rh(NBD)(dppe)+ as the catalyst precursor under intercalated and homogeneous reaction conditions. The yields of terminal olefins are consistently higher for the intercalated catalyst. The deviation from solution yields are larger when the intercalated catalyst is solvated with methanol than with acetone.0 Methanol swells the interlayers to an average thickness of 12 A, whereas acetone swells the interlayers to w 15 A. Since the more constricted methanol solvated interlayers provide the higher yields of terminal olefins, spacial factors as well as polarization effects induced by the charged silicate sheets may be contributing to the deviations from solution behavior. In this reaction system polarization effects may well be more important than spacial factors in directing hydrogenation transfer because the spacial requirements of the transition states derived from or r 3 allyl intermediates should be very similar.

The general idea underlying the preparation of layered clay-polymer intercalates follows the simple rules of ion exchange. In most cases, the synthesis involves either intercalation of a polymer from solution or a suitable monomer followed by subsequent polymerization. But for more technologically important polymers, both approaches are limited since neither a suitable monomer nor a compatible polymer host solvent system is always available. 

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