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Reversing‐pulse electric birefringence of poly(γ‐benzyl‐ L ‐glutamate). III. The temperature dependence of the transient and steady‐state behavior in cyclohexanone
Author(s) -
Yamaoka Kiwamu,
Yamamoto Shinobu,
Ueda Kazuyoshi
Publication year - 1987
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.360260509
Subject(s) - chemistry , birefringence , cyclohexanone , analytical chemistry (journal) , atmospheric temperature range , dipole , field strength , steady state (chemistry) , electric field , anisotropy , thermodynamics , organic chemistry , optics , magnetic field , physics , quantum mechanics , catalysis
Abstract The reversing‐pulse electric birefringence (RPEB) technique was applied to the study of the temperature effect on the electrooptical and hydrodynamic properties of a fractionated [Glu(OBzl)] n sample, which is molecularly dissolved in cyclohexanone. The aim was to develop a standard analytical method for thermal denaturation and temperature‐induced conformational transitions. The field‐on reverse and steady‐state signal, and the field‐off decay signal, were measured at 535 nm and at a constant low field strength (ca. 3 kV/cm) over a wide temperature range (5–90°C). The steady‐state birefringence and the relaxation time in the decay process were also measured at two constant temperatures (5 and 70°C) over a wide field strength range ( E ≤ 20 kV/cm). By the combination of these two different sets of RPEB measurements, the unwanted effect of the high pulse field on polymer conformation at elevated temperatures could be minimized. Together with the density and viscosity of cyclohexanone measured between 5 and 95°C, the following quantities could be evaluated: the weight‐average permanent dipole moment and polarizability anisotropy, the reduced optical anisotropy factor (Δ g / n ), the weight‐average length, and the degree of polydispersity. All these quantities, except for Δ g / n , were found to be almost independent of temperature (5–90°C) and concentration (1.54–4.27 m M ).