A pivotal event in the development of this technology was the disclosure by Toyota of an improved method for producing nylon 6/clay nanocomposites using an in situ polymerization process that effectively exfoliates the aluminosilicate layers by an easily understood chemical mechanism[9]. Since then,similar chemical strategies have been described for manythermoplastic and thermoset polymers. The Toyota process is illustrated schematically in Figure 5. Sodium montmorillonite is mixed with an α, ω-amino acid (e.g., aminolauric acid) in aqueous hydrochloric acid to protonate the aminolauric acid which then can exchange with the sodium counterions; thus,
the alkyl units of the resulting organoclay has terminal carboxyl groups. Under appropriate reaction conditions, the carboxyl groups on the organoclay will initiate ring-opening polymerization of caprolactam to form nylon 6 chains ionically bonded to the aluminosilicate platelets.
