Intercalation strategies in clay/polymer hybrids

Layered silicate clays are natural crystallites and are well recognized for their structures and industrial applications, but there are very few reports on their structural confinement properties and on the mechanisms that underlie their polymer interactions. In this review, we summarize the recent progress on clay modification via conventional ion exchange reactions, sol gel linking, atom transfer radical polymerization, and polymer intercalation. The organic interaction of ionic clays involves different noncovalent bonding forces, such as amido acid five-membered ring chelation, carboxylic acid chelation, intermolecular hydrogen bonding, and double-layer hydrophobic alignment in a layered clay confinement. Controlling the organic species, their amounts and their self-assembled conformation in a clay confinement could lead to the tailoring of the silicate platelet interlayer distance and of their organophilic properties. Furthermore, the layered structure could be totally exfoliated and structurally randomized into individual silicate platelets using different mechanisms, such as the phase inversion of amphiphilic copolymer emulsifiers and phase transitions that involve zigzag Mannich polyamines. For comparison, the organic modification of graphene/graphite plate-like carbonaceous materials is briefly reviewed. The self-organization of organics in clay interlayer galleries and the randomization of layered silicate stacks into platelets are reviewed to understand the noncovalent bonding interactions between the clays and various organics. Different intercalation and exfoliation strategies help the in-depth understanding of clay chemistry and indicate new clay applications. (C) 2013 Elsevier Ltd. All rights reserved.