Abstract
The Birnboim-Schrag multiple-lumped resonator has been used to measure storage (G′) and loss (G″) shear moduli, in the concentration range (c) from 0.0015 to 0.018 g/cc, of a polystyrene of molecular weight 860000 in two θ-solvents (decalin and di-2-ethylhexyl phthalate) and two good solvents (α-chloronaphthalene and Aroclor 1232), as well as a polystyrene of molecular weight 410000 in Aroclor 1232. The frequency range was from 106 to 6060 Hz. Comparison of the initial concentration dependences of G′ and G″ (i.e., the initial slopes of plots of G′/c and G″−ωηs/c, where ω is radian frequency and ηs solvent viscosity), and examination of their changes with frequency, show that the longest relaxation time is affected much more than others by incipient intermolecular interactions. The intercepts, [G′] and [G″], of these extrapolation plots and their frequency dependence can be compared with infinite-dilution theories. In the two θ-solvents, they agree closely with the Zimm theory; the proportionality of relaxation times to ηs and the 23-fold difference in ηs affords an extended scale of reduced frequency. In the two good solvents, they fit the Tschoegl theory with hydrodynamic parameter h=40 and the non-Gaussian parameter e=0.13.
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