Effects of molecular weight and arm number on properties of star-shape styrene–butadiene–styrene triblock copolymer

✍ Scribed by Xiaopeng Xiong; Lina Zhang; Zhaocheng Ma; Yang Li

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 244 KB
• Volume: 95
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.21267

✦ Synopsis

Abstract

A star‐shape styrene–butadiene–styrene triblock copolymer SBS (802) was synthesized and fractionated into four fractions coded as 802‐F1 (four arms), 802‐F2 (two arms), 802‐F3 (one arm), and 802‐F4 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 × 10^4^, 8.2 × 10^4^, 4.3 × 10^4^, and 1.19 × 10^4^, respectively. The samples were, respectively, compression‐molded 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 ^1^H‐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 (σ~b,~ 28.4 MPa) and elongation at break (ε~b~, 1610%), and its optical transmittance is much higher than those of 802C and 802‐F2C. 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. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 832–840, 2005