6533b82dfe1ef96bd12908e0

RESEARCH PRODUCT

Viscosity of Polymer Solutions over the Full Range of Composition: A Thermodynamically Inspired Two-Parameter Approach

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The approach yields the following relation for the relative viscosity η rel as a function of polymer concentration c (mass/volume): ln ηrel = c/(1 + pc + qc2). Reduced concentrations c (defined as c = c[η], where [η] is the intrinsic viscosity) are used instead of c to incorporate thermodynamic information. The parameters p and q account for changes in the free volume of the solvent caused by the polymer. The analysis of literature data for seven very dissimilar systems discloses the following common feature: p > 0 and q < 0. This means that the curves in the plots of ln ηrel as a function of c are normally located below the tangent at low c and above it at high c. The values of p and q correlate strongly with the temperature distance to the glass-transition temperature of the polymer (Tg). Beyond the mere modeling of viscosity data, the approach allows the determination of [η] from data at high polymer concentrations and provides information on the generalized intrinsic viscosity, {η}. Measuremen...