Concentration fluctuations and segmental relaxation in miscible polymer blends

  • C. M. Roland
  • K. L. Ngai
Part of the Progress in Colloid & Polymer Science book series (PROGCOLLOID, volume 91)


Mechanical measurements in the glass transition zone were carried out on a series of polydienes to study the effect of chemical structure on the segmental relaxation. The breadth of the glass transition dispersion in the mechanical spectrum increased with increasing concentration of pendant vinyl groups on the main chain. The broader relaxations exhibited stronger temperature dependences. Both observations are consistent with the compling model of relaxation. Enhanced intermolecular coupling arises due to steric interferences among the vinyl moieties, and the coupling model predicts that more cooperative relaxations will be both broader and more temperature sensitive. In miscible blends the glass transition dispersion is further broadened due the distribution of local environments engendered by concentration fluctuations. The coupling model is extended to consider the effect of concentration fluctuations on the local variation in the degree of intermolecular cooperativity. The shape of the relaxation spectra of miscible blends in the glass transition zone, as well as both composition and temperature dependencies of the dispersion, are markedly influenced by the concentration fluctuations specific to miscible blends. Application of the model to two blends is demonstrated to successfully describe the prominent features of the measurements.

Key words

Miscible blend segmental relaxation concentration fluctuations 


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Copyright information

© Dr. Dietrich Steinkopff Verlag GmbH & Co. KG 1993

Authors and Affiliations

  • C. M. Roland
    • 1
  • K. L. Ngai
    • 1
  1. 1.Naval Research LaboratoryWashington, DCUSA

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