Preparation and dynamic mechanical properties of poly(styrene-b-butadiene)-modified clay nanocomposites

Polybutyl acrylate (PBA) was intercalated into clay by the method of multistep exchange reactions and diffusion polymerization. The clay interlayer surface is modified, and obtaining the modified clay. The structures of the clay-PBA, clay-GA (glutamic acid), and the clay-DMSO (dimethyl sulfoxide) were characterized using X-ray diffraction (XRD). The new hybrid nanocomposite thermoplastic elastomers were prepared by the clay-PBA with poly(styrene-b-butadiene) block copolymer (SBS) through direct melt intercalation. The dynamic mechanical analysis (DMA) curves of the SBS/modified clay nanocomposites show that partial polystyrene segments of the SBS have intercalated into the modified clay interlayer and exhibited a new glass transition at about 157degreesC (T-g3). The glass transition temperature of polybutadiene segments (T-g1) and polystyrene segments out of the modified clay interlayer (T-g2) are about -76 and 94degreesC, respectively, comparied with about -79 and 100degreesC of the neat SBS, and they are basically unchanged. The T-g2 intensity of the SBS-modified clay decreases with increasing the amounts of the modified clay, and the T-g3 intensity of the SBS-modified clay decreases with increasing the amounts of the modified clay up to about 8.0 wt %. When the contents of the modified clay are less than about 8.0 wt %, the SBS-modified clay nanocomposites are homogeneous and transparent. The T-gb and T-gs of the SBS-clay (mass ratio = 98.0/2.0) are -78.39 and 98.29degreesC, respectively. This result shows that the unmodified clay does not essentially affect the T-gb and Tgs of the SBS, and no interactions occur between the SBS and the unmodified clay. (C) 2002 Wiley Periodicals, Inc.