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.