A star-shape styrene- butadiene-styrene triblock copolymer SBS (802) was synthesized and fractionated into four fractions coded as 802-F1 (four arms), 802-172 (two arms), 802-F3 (one arm), and 802-174 by repeating fractional precipitation. Their weight-average molecular weight (M-w) was measured by size-exclusion chromatography combined with laser light scattering to be 16.0 X 10(4), 8.2 X 10(4), 4.3 X 10(4), and 1.19 X 10(4), respectively. The samples were, respectively, compressionmolded and solution-cast to obtain the sheets coded as 802C, 802-F1C, 802-F2C, and 802S, 802-F1S, 802-F2S. The structures and mechanical properties of the sheets were characterized by H-1-NMR, scanning electron microscope, wide-angle X-ray diffractometer, tensile testing, and dynamic mechanical thermal analysis. The results indicated that the compression-molded 802-F1C exhibited the higher tensile strength (sigma(b), 28.4 MPa) and elongation at break (epsilon(b), 1610%), and its optical transmittance is much higher than those of 802C and 802F2C. This work revealed that the star-shape SBS with four arms could be helpful in the enhancement of the properties as a result of good miscibility of the compression-molded SBS sheets. (C) 2004 Wiley Periodicals, Inc.