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

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 ϫ 10 4 , 8.2 ϫ 10 4 , 4.3 ϫ 10 4 , and 1.19 ϫ 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 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 ( b, 28.4 MPa) and elongation at break ( 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.

Preparation and characterization of cellulose and konjac glucomannan blend film from ionic liquid

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Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped trans‐Cinnamaldehyde and Eugenol for Antimicrobial Delivery Applications

“…A simple semi‐empirical equation also used to describe the amount of drug released from a wide variety of matrix delivery systems is the so‐called power law (Costa and others 2001; Zuleger and Lippold 2001; Siepmann and Peppas 2001; Xiong and others 2005; Gamsiz and others 2008). The power law model is similar in form to the short‐time approximation of the exact solution of Fick's second law of diffusion (Ritger and Peppas 1987a; Ritger and Peppas 1987b).…”

Influence of molecular architecture of S–S/B–S triblock copolymers on rheological properties

“…Xiong et al24 investigated star‐shaped SBS triblock copolymers and found that molecular weight, arm number, and processing conditions play an important role in the improvement of their physical properties. Huy et al8 found that the phase diagram of SBS block copolymers can be significantly influenced by the modification of the interfacial structure.…”