Second and Third Virial Coefficients for Polyisobutylene in Heptane, an Intermediate Solvent

Abstract

Light scattering measurements have been made on nine polyisobutylene (PIB) fractions in heptane, an intermediate solvent, at 25°C to determine the second virial coefficient A2 and the third virial coefficient A3 as functions of weight-average molecular weight Mw ranging from 2.7×104 to 7.8×106. For six of the fractions, z-average mean-square radii of gyration have also been determined. In the molecular weight range studied, A2 and A3 vary as Mw−0.21 and Mw0.58, respectively, and the factor g defined by A3/A22Mw is about 0.33 almost independent of molecular weight. The data of g and Ψ (the interpenetration function) as functions of the cube of the radius expansion factor αS, combined with previous data in cyclohexane, a good solvent, show that the two-parameter theory breaks down unless αS3 is larger than about 2 for g and about 5 for Ψ. It is concluded from the comparison of these g data with the recent theory of Norisuye et al. that the failure of the two-parameter theory for g at small αS3 is due primarily to the neglect of three-segment interactions and that the effect of chain stiffness on g in heptane is of minor importance in the Mw range studied. On the other hand, the stiffness effect on Ψ for PIB is found to be remarkable even at large αS3. In fact, the different dependences of Ψ on αS3 observed for heptane and cyclohexane solutions are explained semiquantitatively by the Yamakawa theory which takes account of the stiffness effect within the binary cluster approximation.

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Akasaka, K., Nakamura, Y., Norisuye, T. et al. Second and Third Virial Coefficients for Polyisobutylene in Heptane, an Intermediate Solvent. Polym J 26, 1387–1395 (1994). https://doi.org/10.1295/polymj.26.1387

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Keywords

  • Second Virial Coefficient
  • Third Virial Coefficient
  • Polyisobutylene
  • Excluded-Volume Effect
  • Expansion Factor
  • Three-Segment Interaction
  • Light Scattering

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