The chemistry of polymer-clay hybrids

There are many organic-inorganic hybrid materials, or molecular composites, in biomineral systems such as bones, teeth, shells and so on. Owing to their complexity a synthetic approach to these materials has not fully developed. Recently, however, synthetic methods have been proposed to prepare artificial organic-inorganic hybrid materials. One is the sol-gel method using metal alkoxides and organic molecules. Another method is the utilization of intercalation reactions of clay minerals. In this paper we review our research in the latter field. We have prepared several polymer-clay hybrids, in which polymers are nylon 6, nitrile rubber and others. They, when molded, have excellent mechanical, thermal and chemical properties compared with unfilled polymers and/or conventional composites. Syntheses, structures and application of the hybrids are presented. In the hybrids negatively charged silicate (clay mineral) and positively charged polymer-ends are directly bonded through ionic bonds. The mechanism of reinforcement is also discussed with the results of CP-MAS NMR and pulsed NMR studies.