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Second virial coefficient revisited, 3. Viscosity of dilute polymer solutions: Molecular weight dependence of the Huggins coefficient

1986; Wiley; Volume: 187; Issue: 12 Linguagem: Inglês

10.1002/macp.1986.021871221

0025-116X

F. Gundert, Bernhard Wolf,

Material Dynamics and Properties

Abstract The variation of the Huggins coefficient K H with the relative molecular mass M of the polymers was measured for solutions of polystyrene and of polyisobutylene and found to be most pronounced in the case of thermodynamically good solvents but vanishing at the theta‐temperature, where the individual curves k H ( T; M ) intersect with each other. The experimental results are interpreted as a consequence of the rheological inequality of inter‐ and intra‐molecular contacts between polymer segments. A model is presented according to which k H should be a linear function of M − ( a −0,5) , where a is the exponent of the intrinsic viscosity‐relative molecular mass relationship (Kuhn‐Mark‐Houwink). The evaluation of the present data, together with information from the literature, yields the individual effects from inter‐ and intra‐molecular intersegmental contacts, their interdependence, and their variation with the thermodynamic quality of the solvent. In thermodynamically poor solvents, were the polymer coils are nondraining, these effects are found to differ extremely; however, they approach each other as the goodness of the solvent improves and the coils become draining; their identity can be extrapolated for a = 1.