The pillaring effect of the 1,2-dimethyl-3(benzyl ethyl iso-butyl POSS) cation in polymer/montmorillonite nanocomposites
Douglas M. Fox, Richard H. Harris Jr., Jeffrey W. Gilman
The use of natural and non-toxic compounds to improve the properties of polymers has received significant attention over the past decade. In this study, a polyhedral oligomeric silsesquioxane (POSS) tethered imidazolium surfactant was used to exchange montmorillonite for the preparation of polymer nanocomposites in polystyrene, poly(ethylene-co-vinyl acetate), and polyamide 6 using a melt blending technique. Simultaneous temperature resolved small angle x-ray scattering and wide angle x-ray diffraction was used to monitor the surfactant stability and phase behavior within the clay galleries as the temperature rises above the melting point (processing temperature) of polyamide 6. Good thermal stability of the surfactant was in agreement with thermogravimetric analysis of the clays and polymer nanocomposites. Modest improvements in the polymer nanocomposites were also observed. Transmission electron microscopy revealed a mixed intercalated/exfoliated structure, with the presence of small tactoids exhibiting gallery spacings greater than 3.8 nm in all three polymers. Fluorescent tagged organically exchanged montomorillonite was used to assess the quality of nanoparticle dispersion using laser scanning confocal microscopy and ultraviolet fluorescence spectroscopy. Results indicate that the tactoids are well dispersed throughout the polymer matrix. Exchanging the montmorillonite with lower loadings of the POSS surfactant slightly increased the size of clay tactoids, but did not significantly alter the gallery spacing or overall dispersion of these particles on the meso-scale. The results suggest that the bulky and rigid structure of POSS as well as its tendency to aggregate into ordered crystals form a bi-layer structure in the clay galleries and prevent montmorillonite from completely exfoliating, even in polyamide 6
POSS, montmorillonite, nanocomposites, intercalation, fluorescent microscopy, temperature resolved x-ray
, Harris, R.
and Gilman, J.
The pillaring effect of the 1,2-dimethyl-3(benzyl ethyl iso-butyl POSS) cation in polymer/montmorillonite nanocomposites, Polymer
(Accessed November 30, 2023)