Preparation of the polymer-clay nanocomposites in exfoliated state by interface stabilization

To suppress the repulsive interfacial energy between hydrophilic clay and a hydrophobic polymer matrix for polymer-clay nanocomposites, a third component of amphiphilic nature such as poly(epsilon-caprolactone) (PCL) was introduced into the styrene-acrylonitrile copolymers (SAN)/Na-montmorillonite system. Once epsilon-caprolactone was polymerized in the presence of Na-montmorillonite, the successful ring-opening polymerization of epsilon-caprolactone and the well-developed exfoliated structure of PCL/Na-montmorillonite mixture were confirmed. Thereafter, SAN was melt-mixed with PCL/Na-montmorillonite nanocomposite, and the SAN matrix and PCL fraction were completely miscible to form a homogeneous mixture with retention of the exfoliated state of Na-montmorillonite, exhibiting that PCL effectively stabilizes the repulsive polymer-clay interface and contributes to the improvement of the mechanical properties of nanocomposites. (C) 2003 Wiley Periodicals, Inc.