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Infinite‐dilution viscoelastic properties of poly‐γ‐benzyl‐ L ‐glutamate in helicogenic solvents
Author(s) -
Warren Thomas C.,
Schrag John L.,
Ferry John D.
Publication year - 1973
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1973.360120816
Subject(s) - viscoelasticity , chemistry , relaxation (psychology) , dilution , thermodynamics , range (aeronautics) , analytical chemistry (journal) , computational chemistry , polymer chemistry , organic chemistry , composite material , physics , materials science , psychology , social psychology
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.