Reversing-pulse electric birefringence of poly (γ-benzyl-L-glutamate). II. Field-strength dependence of steady-state and decay signals of well-fractionated samples

The electric field dependence (up to 21 kV/cm) of the steady-state and decay signals has been examined on the four well-fractionated samples of poly(γ-benzyl-L -glutamate), Glu(OBzl)]_n, in N,N-dimethylformamide at 535 nm and 20°C. Together with the data previously obtained from the reversing-pulse electric birefringence Ueda, K., Nomura, M. & Yamaoka, K. (1983) Biopolymers 22 , 2077–2090], the steady-state birefringence and field-free relaxation time were analyzed by a method that takes into account the polydispersity of the chain length. The weight-average chain length, (l_w), permanent dipole moment, (μ_w), electric polarizability anisotropy, (Δα_w), and the length-independent optical anisotropy factor were evaluated. The axial translation per residue was calculated for the Glu(OBzl)]_n helix, but the uncertainly involved in the weight-average molecular weights, determined from light scattering by different investigators, makes the determination of the exact conformation of Glu(OBzl)]_n difficult. The contribution of Δα_w to electric field orientation was found to be significant, since Δα_w was approximately proportional to l_w. A linear relationship also exists between μ_w and l_w, when the Glu(OBzl)]_n helix is shorter than about 1200 Å.