Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin-screw extruder. The effect of molecular weight of PP-MA (maleic anhydride-modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP-MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X-ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP-MA330k/clay, a well-dispersed two-component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP-MA330k/clay, an intercalated three-component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content.

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Fluorescence decay and polarization of dansyl-labeled poly(methacrylic acid) (PMA) and poly-(acrylic acid) (PAA) have been studied as a function of pH. The decay measurements have shown that, at low pH, PMA chains form highly compact hydrophobic clusters, which are joined by short extended polymer chains. During the transition from the compact to the expanded form, the size of the clusters decreases up to a limit, beyond which the clusters disintegrate completely to an expanded polymer chain. The effect of PMA molar mass and ionic strength on this process was investigated.

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