Nano Trends: A Journal of Nanotechnology and Its Applications Volume 16, Issue 2, ISSN: 0973-418X ©NSTC (2014) 13-29 © STM Journals 2014. All Rights Reserved Page 13 Effect of Layered Double Hydroxide in Polymer Nanocomposites: The Review Pon Maheskumar, P. Sathish Kumar, P. Sathiamurthi, R. Rajasekar* Department of Mechanical Engineering, School of Building and Mechanical Sciences, Kongu Engineering College, Tamilnadu-638052, India Abstract Layered double hydroxides (LDH) are mineral and synthetic materials with positively charged brucite-type layers of mixed metal hydroxides. Inorganic nanoscale fillers are considered to be very important to include layered silicates, nanotubes, metal oxides, nanoparticles of metals, semiconductors, carbon black, etc. Due to this reason, nanocomposites have been developed using LDH for several applications. Main emphasis has been accorded to the preparation and characterization of LDH nanocomposites utilizing various industrial polymers for wide applications in fire safety materials, sensors, bio-medical, packing, electrical cables, etc. In this review, the morphological characterization exploring the interaction and extent of dispersion of LDH in the polymer matrices are extensively accounted. From the reports, it clearly proves the exfoliation and strong interaction of LDH extremely enhanced the physical, mechanical, thermal, biocompatibility and tribological properties of the added polymer. LDHs have been shown to have remarkable shape-selective intercalation properties. Keywords: Layered double hydroxide polymer nanocomposites, thermal stability *Author for Correspondence E-mail: rajasekar.cr@gmail.com INTRODUCTION LDH is a class of 2D-nanostructured anionic clays. LDHs are lamellar-mixed hydroxides containing positively charged anions and water molecules intercalated between the layers [1]. The most interesting property of LDH is the high anion exchange capacity for various water contaminants. LDH is commonly represented by the formula (M z+ 1−x M 3+ x (OH) 2 ) q+ (X n− ) q/n yH 2 O [2], where M 2+ and M 3+ are di and trivalent cations and A n− is the interlayer anions which balance the positive charges on the layers and x is defined as the molar ratio [3]. LDHs are formed widely with a variety of anions X (e.g., Cl − , Br − , NO 3 − , CO 3 2− , SO 4 2− and SeO 4 2− ) and various other divalent metal ion such as Mg 2+ , Co 2+ , Ni 2+ , Cu 2+ , or Zn 2+ and trivalent metal ion such as Al 3+ , Fe 3+ , Mn 3+ , or Cr 3+ in the hydroxide layers [4]. In recent years many researches devoted to identify the ability of LDH to remove harmful oxyanions such as arsenate, phosphate, chromate, etc., from contaminated waters by both anion exchange and surface adsorption of the oxyanions for interlayer anions in the LDH structure [5]. The structure of most of the mineral hydrotalcite (HT) which is of a natural magnesium–aluminum hydroxycarbonate is Mg 6 Al 2 (OH) 16 CO 3 4H 2 O [6]. These compounds consist of positively charged brucite-type octahedral sheets and alternating with interlayers containing carbonate anions in the natural mineral or other exchangeable anions [7]. When LDH is treated in high temperature it decomposes into mixed metal oxide solid and the calcined product can reconstruct its original layered structure via rehydration and simultaneous incorporating of anions into the interlayer from the aqueous solution. Significant progress has been made in the synthesis of LDH with new compositions and morphologies over the last decade allowing improved applications in many areas. Synthesizing LDH with various combinations of divalent and trivalent metals and changing its metal compositions are relatively simple. LDH has advances in environmental, catalytic,