Effect of Textured Surfactant Brushes on Polymer-Layered Silicate Nanocomposite Morphology

Report No. ARL-TR-3136
Authors: Mary K. Kurian, Arnab Dasgupta, Mary E. Galvin, and Frederick L. Beyer
Date/Pages: February 2004; 24 pages
Abstract: The morphological behavior of a series of polymer-layered silicate nanocomposites (PLSNs) has been investigated. The goal was to probe the effect of ?textured? silicate surfaces on PLSN morphology. The nanocomposites were fabricated by mixing montmorillonite clay that was carefully modified with tailor-made polystyrene (PS) surfactants into a PS homopolymer matrix, where the chemical similarity of the matrix polymer and surfactants ensures complete miscibility of surfactant and homopolymer. To examine the effect of silicate surface ?texture,? clay was modified with combinations of long and short surfactants. The samples, characterized by small-angle x-ray scattering (SAXS), were then melt-annealed to allow the equilibrium morphology to develop. Based on the implications of the Balazs model and other work on the wetting behavior of polymer melts, textured surfaces were expected to promote the intercalation of the homopolymer matrix material into the modified clay. Extensive characterization of both the modified clays as well as the resultant nanocomposites clearly showed that the modified clays exhibited a high degree of order, but also that only phase-separated morphologies were formed in the corresponding nanocomposites.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2004