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By assuming simplified hypotheses which result from the molecular analysis of Doi-Edwards, it is possible to propose rheological methods for characterizing molar weight distribution of entangled polymeric liquids. The generalized exponential distribution is especially concerned. Theoretical expressions of rheological parameters are derived, and their numerical values are calculated in special cases. A numerical method of discrimination and identification of these special distributions is proposed. [ABSTRACT FROM AUTHOR]

The polydispersity of the molar mass of a material influences the behaviour of its dynamic rheological properties G′ (ω) and G″ ( ω). This is exemplified by the deviation from unity of the index I = [2 − ( d log G′/d log ω)]/[1 − ( d log G″/d log ω)] in the terminal zone, i.e. at low frequencies. For a normal logarithmic distribution of species, a quantitative correlation may be established between the rheological properties and the parameter that is characteristic of the polydispersity for these species. This correlation can, in certain cases, be drawn from measurements in just the terminal zone or it may require measurements both in the terminal zone and at the beginning of the plateau zone. In each case, the parameter of dispersion can be determined by simple graphical or numerical methods. Finally, an example of the application of these methods to entangled liquid polymers is presented. [ABSTRACT FROM AUTHOR]