Molecular architectures of four‐arm star‐shaped styrene‐butadiene copolymer

Abstract

AbstractTo understand the molecular architectures of styrene‐butadiene four‐arm star (SBS) copolymers, a size exclusion chromatography combined with laser light scattering (SEC‐LLS) has been used to determine their weight‐average molecular weight (Mw) and radius of gyration (〈S2〉1/2), and a new method for the establishment of the Mark‐Houwink equation from one sample has been developed. Based on the Flory viscosity theory, we successfully have reduced the 〈S2〉1/2 values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities ([η]). For the first time, the dependences of 〈S2〉1/2 and [η] on Mw for the four‐arm star SBS in tetrahydrofuran at 25°C were found, respectively, to be 〈S2〉1/2 = 2.62 × 10−2 M (nm) and [η] = 3.68 × 10−2 M (mL/g) in the Mw range from 1.4 × 105 to 3.0 × 105. From data of [η] and 〈S2〉1/2 for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g′) of 〈S2〉 and [η] for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 961–965, 2005