Polymer interleaved layered double hydroxide: A new emerging class of nanocomposites

The present paper describes the synthesis and characterization of nanocompo site materials built from the assembly of organic polymers and two-dimensio nal host materials, particularly reviewing those composed of layered double hydroxide (LDH) inorganic frameworks. When the meaning commonly adopted fo r nanocomposites is narrowed, the system is constituted of sheets lying on top of each other in which covalent forces maintain the chemical integrity and define an interlamellar gap filled up with the polymer guest. The situa tion is different from an inorganic filler dispersed into a polymeric matri x. The incorporation of polymer between the galleries proceeds via differen t pathways such as coprecipitation, exchange, in situ polymerization, surfa ctant-mediated incorporation, hydrothermal treatment, reconstruction, or re stacking. The latter method, recently effective via the exfoliation of the LDH layers, appears to be more favorable, in terms of crystallinity, to cap ture monomer entities than the whole polymer. The nanocomposites are enlist ed according to the preparation pathways. It is found that these multicompo nent systems are thermally more stable than the pristine inorganic compound s, leading, for example, to potential applications in flame-retardant compo sites. A large variety of LDH/polymer systems may be tailored considering t he highly tunable intralayer composition coupled to the choice of the organ ic moiety. The paper concludes with a brief discussion underlining the pers pectives. Despite their appeal, the polymer/LDH class of nanocomposites has not yet been extensively studied for applications.