6533b7d8fe1ef96bd12696ff

RESEARCH PRODUCT

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Sedimentation coefficients of S of polystyrene covering a broad range of molecular weights M, are measured in toluene and 2-butanone in the semidilute regime. The results are compared with literature data using a plot of S · NA · η/(1 − νρ) = M · η/f versus concentration c, allowing experiments in different solvents of different density ρ and viscosity η to be compared (ν: partial specific volume of polymer; f: friction coefficient; NA: Avogadro number). According to scaling theory for concentrations higher than a critical concentration c, linear plots are to be expected. This is true for the theta-solvent cyclohexane, but for the theta-solvent cyclopentane as well as for the thermodynamically semi-good and good solvents bent curves are obtained, the slopes of which turn toward a limiting value for high M and low c. The theoretical values of the slope for theta-solvents (−1) is well represented by both theta-solvents. For the semi-good and good solvents the experimental limiting slopes are (slightly) lower than the predicted ones. With samples of still higher M becoming available this difference might become more pronounced.