The first clay nanocomposite studied is also the first clay nanocomposite to be commercialized.  The work was begun in the 1980's by researchers at Toyota's Central Research and Development Laboratories1.  Montmorillonite clay was exchanged with the acid species shown below.

This quaternary ammonium ion replaced the cations on the clay surface, swelling the clay and allowing the clay to mix with e-caprolactam.  The caprolactam was then polymerized to form nylon-6.
    The nylon-6/clay nanocomposite formed through ring-opening had some considerable property improvements over ordinary nylon-6.  The new material is now being used by Toyota for tough, heat resistant, nylon timing belt covers.

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1.  Gilman, Jeffrey W. et al.  Nanocomposites:  A Revolutionary New Flame Retardant Approach.