Organic Modification of LDHs

To obtain good dispersion in polyolefin matrices, the organic modification of LDH is necessary before using it as nanofiller. Generally, there are several modification methods for preparing organic modified LDH they are as follows ... 

The organic modification of LDHs is an inevitable step in the process of polymer nanocomposites preparation. Therefore, the intercalated anions are important to the dispersion of LDHs and the resulting fire properties. Zammarano et al. [98] examined the effect of two organic modifiers, 3-aminobenzenesulfonic acid (ABS) and 4-toluenesulfonic acid monohydrate (TS), on the structure and properties of epoxy/LDH composites. Because of their reactivity with epoxy, ABS-modified LDHs (LDH-ABS) had better dispersion than LDH-TS. As a result, epoxy/LDH-ABS showed a greater reduction in PHRR (51%) than epoxy/LDH-TS at the same LDH loading. 

The surface modification of LDHs with organic molecules has recently been investigated [42,143]. It has been reported, for example, that the product of the reaction of a ZnAl(OH) LDH with an organic oxychloride is an esterified LDH, with the organic molecules attached directly to the matrix cations (i.e. not through the surface OH groups) [144-146]. Similarly, the preparation of modified MgAl- and ZnAl-LDHs, in which alkyl and aryl phosphonate anions... 

At variance with the high number of applications of cationic clays as pre-concentrating materials, only a few examples are found about the use of anionic clays [77-79]. They involve both LDHs as such, for the adsorption of electroactive anions [76], and the modification of conventional anionic clays for the analysis of organic species in this last case, anionic surfactants are adsorbed in the interlayer region of the clay, to increase the distance between adjacent brucite-like layers and to induce a higher hydrophobic character that is more suitable for the adsorption of organic species [84, 85]. 

L. C. Du, B. J. Qu, and M. Zhang, Thermal properties and combustion characterization of nylon 6/MgAl-LDH nanocomposites via organic modification and melt intercalation. Polymer Degradation and Stability, 92 (2007), 497-502. 

The high diversity in metal use and possible organic modification leads to an escalating number of publications in the last years. In 199010 articles, in 2000132 articles, and in 2009 552 articles are recorded by web of science dealing with the preparation and use of hydrotalcite and similar layered stmctures. Therefore in this chapter only some aspects dealing with LDH nanocomposites can be highlighted. 

Conductive electrodes based on metal oxide, e.g., indium-tin oxide (TTO), are widely used in electrochemistry as a support for surface modification with the goal to develop sensors with electrochemical transduction or combined spectroscopic and electrochemical responses or electrochemiluminescence. Inorganic thin films can also be prepared from the assembly of two-dimensional layered inorganic solids, such as cationic clays and layered double hydroxides (LDHs, also defined as anionic clays). These materials can be used to preconcentrate species on the basis of ion-exchange reactions and applied to heavy metal determination or for the detection of organic pollutants. 

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