Xiong, X., Eckelt, J., Wolf, B.A., Zhang, Z., Zhang, L.
"Continuous spin fractionation and characterization by size exclusion chromatography for styrene-butadiene block copolymers"
Journal of Chromatography A , submitted .
Abstract: Linear and star-shaped styrene-butadiene block copolymers synthesized by anionic polymerization of butadiene and styrene were fractionated by applying a newly developed large-scale fractionation technique, named continuous spin fractionation (CSF). Their molecular weight and polydispersity index (d= M-w/M-n) were measured with size-exclusion chromatography and static light scattering. For the linear triblock copolymer a fractionation via temperature variation turned out to be better suited than the usual isothermal procedure. The star-shaped polymer with the d value of 1.33 was fractionated in two CSF steps to get the targeted sample, which has a considerably more uniform structure and a narrower molecular weight distribution (d= 1.11). The corresponding starting linear diblock copolymer was fractionated in one step reducing d from 1.68 to 1.17. With one set of simple laboratory equipment, I kg polymer can be fractionated per day. Utilizing CSF, for the first time, we fractionated successfully the block copolymers. (c) 2006 Elsevier B.V. All rights reserved.
preprint number: 276