Abstract
The viscoelastic behavior of macrocyclic polystyrene fractions having molecular weights ranging from 1.9 x 104to 3.9 x 105 was studied. Measurements of zero shear viscosity and recoverable compliance were made on Strasbourg fractions, Akron fractions, and two of the former which were refractionated. Also, studies of the effects of blending of up to 15.8% linear chains with the refractionated Strasbourg fractions were carried out. These studies show that the presence of linear chain contaminants in the macrocyclic fractions has the effect of decreasing the plateau compliance, JN° = 1/GN°, and increasing the steady-state value of the recoverable compliance Je°. Also, the presence of small amounts of linear contaminant increases dramatically the viscosity of the cyclic fractions. The recovery response of the cyclic fractions was used to qualify those having molecular weights above 44 000 as “good”, “moderate”, or “poor” cycles. The results of analysis of the good and moderate fractions give a picture of the cycles as showing “classical” viscoelastic behavior; i.e., the steady-state recoverable compliance increases with increasing molecular weight and attains a constant value at high molecular weights (Mw> 1.8 x 106), as do linear polymers. The plateau compliance of the cycles is about 2 times that of the linear chains. The limiting value of the steady-state recoverable compliance of the rings is also approximately 2 times that of the linear polymer. We find that the zero shear viscosity-molecular weight relation is well described by an equation of the form η = AM + BMa where α ≃ 3.9, which is somewhat higher than the 3.4 power obtained for entangled linear chains. Results from dilute solution characterization of the Akron cycles are presented and compared with literature values. Anomalies in the behavior are discussed and the use of dynamical properties in dilute solution as a means of determining the quality of cyclic fractions is questioned. © 1989, American Chemical Society. All rights reserved.