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Infinite-dilution viscoelastic properties of poly-γ-benzyl-L-glutamate in helicogenic solvents

✍ Scribed by Thomas C. Warren; John L. Schrag; John D. Ferry

Publisher
Wiley (John Wiley & Sons)
Year
1973
Tongue
English
Weight
558 KB
Volume
12
Category
Article
ISSN
0006-3525

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✦ Synopsis

Abstract

The storage and loss shear moduli, G, and G˝, have been measured for solutions of three samples of poly‐γ‐benzyl‐L‐glutamate with molecular weights from 16 to 57 × 10^4^, by use of the Birnboim‐Schrag multiple‐lumped resonator. The frequency range was 106 to 6060 H~z~, the concentration range 0.0015–0.005 g/ml, and the temperature 25°C. Two helicogenic solvents with widely different viscosities, dimethylformamide and m‐cresol, were used to provide a broader effective frequency range. The intrinsic moduli, extrapolated to infinite dilution, were compared with the predictions of the theory of Ullman for rigid rods; agreement was rather good at the lowest frequencies, but unsatisfactory at high frequencies. The data over the entire frequency range of three of logarithmic decades could be described closely by a relaxation spectrum consisting of one terminal relaxation time separated by a gap from a sequence of relaxtion times spaced as in the Zimm theory. The terminal time agrees approximately with that calculated for end‐over‐end rotation of a rigid rod. The additional relaxation mechanisms are tentatively attributed to modes of flexural deformation of the helix.

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