Viscosity of fractions from end‐linked polystyrene star macromolecules

Abstract

AbstractA number of OH‐terminated three‐arm star molecules were prepared by anionic polymerization with a specially functionalized initiator. The stars were crosslinked over the OH groups with varying amounts of toluene‐2,4‐diisocyanate. The samples were fractionated by size exclusion chromatography (SEC) on‐line with a low angle laser light scattering (LALLS) and a viscosity (VISC) detector. The Kuhn—Mark—Houwink—Sakurada (KMHS) relationships from the various samples resulted in a common relationship. Shrinking parameters g′j≡[η]j,b/[η]j,lin were determined for each slice and could satisfactorily be interpreted on the basis of the Zimm—Stockmayer theory in connection with a suggestion by Kurata et al. The Kurata suggestion was checked with data from star molecules. The examination revealed that randomly branched and star‐branched macromolecules exhibit significantly different hydrodynamic behavior. The ratio of the Fox—Flory coefficients Φb/Φlin in the relationship [η] = Φ(R/M) increases in both cases with branching. This is a consequence of the enhanced segment density and the resulting increase in the hydrodynamic interaction.