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Polymers and Thermodynamics

Ronald Koningsveld ; Polymer Science and Engineering, University of Massachusetts, Amherst, Mass. 01003, USA, and Max-PLanck-Institute for Polymer Research, D-6500 Mainz, GFR
Ludo A. Kleintjens ; DSM Research and Patents, P. O. Box 18, 6160 MD Geleen, Netherlands
Erik Nies ; Polymer Technology, University of Technology, Eindhoven, Netherlands

Puni tekst: engleski pdf 13.608 Kb

str. 53-89

preuzimanja: 241



Classic thermodynamic equilibrium considerations, supported
by simple molecular models, may lead to useful predictions about
phase relationships in partially miscible systems that contain polymers. How quantitative the prediction is depends on the amount
of experimental information, as well as, on the complexity of the
system. The solubility parameter and group contribution approaches
present the first LeveL and allow a qualitative judgement whether a system is miscible or not. On this level, the entropy of mixing is not considered though it is higly important. A second, higher level of prediction is supplied by the Flory-Huggins-Staverman equation which permits estimations of the temperature and chain length dependence on the location of miscibility gaps. On this level the concentration ranges of partial miscibility are not well covered. Taking account of the ever present disparity in size and shape between molecules and repeat units improves the situation considerably and represents a third level of prediction. On this level the influence of pressure can reasonably accurately b~ dealt with. If predictions of a high precision are required, the present-day theory fails, even in the simple case of a linear, apolar homopolymer solution. Extensive measurements then remain needed to determine the many empirical and theoretical parameters. Predictions on such a high level have amore than academic value, since they may supply better mathematical frameworks to be applied in less demanding calculations.

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