Layered double hydroxides modification

The dispersion and solid-state ion exchange of ZnCl2 on to the surface of NaY zeolite by use of microwave irradiation [17] and modification of the surface of active carbon as catalyst support by means of microwave induced treatment have also been reported [18]. The ion-exchange reactions of both cationic (montmorillonites) and anionic clays (layered double hydroxides) were greatly accelerated under conditions of microwave heating compared with other techniques currently available [19.]... 

Keywords Layered double hydroxides Layered silicates Nanocomposites Organic modification Reinforcement Rubber Rubber curatives... 

Provided in this chapter is an overview on the fundamentals of polymer nanocomposites, including structure, properties, and surface treatment of the nanoadditives, design of the modifiers, modification of the nanoadditives and structure of modified nanoadditives, synthesis and struc-ture/morphology of the polymer nanocomposites, and the effect of nanoadditives on thermal and fire performance of the matrix polymers and mechanism. Trends for the study of polymer nanocomposites are also provided. This covers all kinds of inorganic nanoadditives, but the primary focus is on clays (particularly on the silicate clays and the layered double hydroxides) and carbon nanotubes. The reader who needs to have more detailed information and/or a better picture about nanoadditives and their influence on the matrix polymers, particularly on the thermal and fire performance, may peruse some key reviews, books, and papers in this area, which are listed at the end of the chapter. 

Layered double hydroxides (LDHs), also known as host-guest layered nanoparticles, were investigated for a variety of biomedical applications, due their ease of synthesis, low cost and good compatibility. The modification of the hydro)yl-rich surface of LDHs with an ATRP initiator was used as a strategy to prepare LDH-based gene delivery vectors, as shown in Scheme 3.26. Surface-initiated ATRP of DMAEMA on a LDH surface... 

An original method to fabricate oxide nanostructured magnetic materials has been proposed in Ref. [328]. The method is based on chemical modification of ion-substituted layered double hydroxides. These structures are nanocomposites based on ferromagnetic y-Fe203 nanoparticles and diamagnetic matrix, which are stable in air and have sufficient coercive force and saturation magnetization of y-Fe203. 

This move from the modification of electrodes to the modification of nonconducting surfaces in contact with electrodes is also seen in systems in which electrodes are modified using nonconduct ive particles. For example, Zak and Kuwana showed that the basic surface of alpha-alumina imbedded in glassy carbon electrodes caused catalysis of the electrooxidation of catechol and other organic species requiring loss of a proton for their oxidation JJ ), Similar results were obtained by Shaw and Creasy (78) using alumina or layered-double hydroxides in composite electrodes (vide infra). 

Other inorganic nanodimension particles such as layered doubled hydroxides, multiwall carbon nanotubes, POSS, and nanographite can also be potential nanoclay-sized flame retardant additives. Chemical compatibility of these materials is possible with surface modification reactions. Char formation is also observed in some plastic matrices. To have commercial value, general cost and easy processing have to be achieved. 

C. Nyambo, D. Chen, S. P. Su, and C. A. Wilkie, Does organic modification of layered double hydroxides improve the fire performance of PMMA Polymer Degradation and Stability, 94 (2009), 1298-1306. 

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. 

In addition to MMT and other cationic clays, layered double hydroxides (LDHs) with the hydrotalcite-type structure are another family of layered materials [18] which, despite they have been used in a lesser extent than MMT (and structure-related materials) as nanocomposite polymer fillers, have shown enormous more potentially advantages than natiual clays, specially concerning their purity and crystallinity and particle size control in addition, they can be also easily functionalized in different ways with different agents, thus permitting a chemical modification of the layers environment to optimize their compatibility with the polymer [19,20]. 

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