Viscoelastic Properties of Dilute Solutions of Random Coil Polymer and α-Helix Polymer

Abstract

The complex rigidities and the complex dynamic viscosities of the solutions of polyisobutylene (PIB) in cyclohexane and those of the solutions of poly-γ-methyl-D-glutamate (PMDG) in chloroform were measured at frequencies of 19.6kc, 39.2kc, and 117.7kc, respectively. The relaxation times corresponding to the longest mode of chain motion were obtained from the steady shear viscosity measurements. All the measurements were performed within the concentration range about 0.1 to 0.5g/dl and at temperature of 15.0 and 30.0°C.The intrinsic quantities were obtained by extrapolating the measured values to zero concentration, and they were compared with the molecular theories of viscoelastic properties for different conformations in the form of normalized dispersion curves, which were obtained by plotting [G']M/RT, [C]M/RT, [η']/[η], and [η]/[η] against the generalized relaxation time (τ1)0/K1=[η]ηsM/RT.The results obtained for PIB in cyclohexane solution show that the experimental values lie between two theoretical dispersion curves by Rouse and Zimm in the four plots for [G'], [G], [η'] and [η]. This means that the effect of the hydrodynamic interaction is not negligible (partial free draining) for the system of this random coil polymer.Results obtained for poly-γ-methyl-D-glutamate in helix solvents show qualitative agreement with the Kirkwood-Auer theory for rod-like polymers.