A Novel Route to Inducing Disorder in Model Polymer-Layered Silicate Nanocomposites

Abstract

The effects of the degree of silicate surface modification by organic surfactants and the nature of surfactant−matrix enthalpic interactions on polymer-layered silicate nanocomposite (PLSN) morphology have been systematically investigated. Using cation exchange to modify montmorillonite, a series of “partially” modified clays were prepared and used in turn to fabricate polystyrene (PS)−, poly(vinyl methyl ether) (PVME)−, and poly(methyl methacrylate) (PMMA)−matrix PLSNs via static melt intercalation. Small-angle X-ray scattering and transmission electron microscopy revealed that the morphological behavior of the PS-based “partial” coverage PLSNs was seemingly dependent on surfactant length, with the shortest surfactant providing the most significant disruption of the clay tactoids. Examination of the PMMA- and PVME-based PLSNs indicated that the nanocomposite morphology was only weakly affected by the nature of matrix−surfactant enthalpic interactions. The results of modifying montmorillonite with 5.5 kg/mol PS-based surfactant at only 4.7% coverage and subsequent fabrication of PLSNs via static melt intercalation confirmed that clay tactoids can be disordered through appropriate control of the degree of surfactant coverage for a given surfactant length.