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

摘要

To 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 (M-W) and radius of gyration ()(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 (1/2) values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities (eta). For the first time, the dependences of 1/2 and eta on M-W for the four-arm star SBS in tetrahydrofuran at 25 degrees C were found, respectively, to be (S-2 1/2 = 2,62 X 10(-2) M (nm) and eta = 3.68 X 10(-2) M-W(0.64) (mL/g) in the M-W range from 1.4 X 10(5) to 3.0 X 10(5). From data of eta and (1/2) for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g') of and eta for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. (c) 2005 Wiley Periodicals, Inc.