CONCENTRATION-DEPENDENCE OF THE VISCOELASTIC PROPERTIES OF POLYSTYRENE-TRICRESYL PHOSPHATE SOLUTIONS

Based on creep and creep-recovery measurements, the viscoelastic functions left bracket J(t), J//r(t), J prime ( omega ), J double prime ( omega ), G prime ( omega ), and L(ln tau ) are presented for solutions of a narrow molecular-weight-distribution polystyrene in tri-m-tolyl phosphate in the concentration range of 1% to 100% polymer. For concentrations of 25% polymer and above, two maxima are exhibited by the retardation spectrum, L(ln tau ). In the neighborhood of each of the maxima the retardation spectra of the more concentrated solutions can be superimposed by translations along both the logL and log tau axes. Reflecting the increasing width of the rubbery plateau with increasing polymer concentration, the dependence of the concentration time-scale shift factors is greater for the terminal region of response. The response of the solvent is seen at the lower concentrations and it is a less sensitive function of the concentration than that of the polystyrene. This behavior is associated with the previously reported observation of two glass-transition temperatures in the middle concentration range. For the higher concentrations, both the steady-state and rubbery-plateau compliances are inversely proportional to the square of the concentration.