Reversing‐pulse electric birefringence of poly(γ‐benzyl‐L‐glutamate). I. Transient behavior of fractionated samples in the low electric field region

Abstract

SynopsisReversing-pulse electric birefringence (RPEB) was measured for the first time for four fractionated poly(y-benzyl-L-glutamate), [Glu(OBzl)],, samples in NJ-dimethylformamide (DMF) at 20°C and a t 535 nm. The RPEB signal showed a deep minimum for each sample on reversal of an applied electric field. The profiles of the reverse-transient signal were analyzed by taking into account the polydispersity for the continuous distribution of molecular lengths. The best set of three quantities (Lw, lw/ln, (&,)2/2rw), which determine a signal profile, was evaluated for each sample. By combining the experimental data of intrinsic viscosity and RPEB, the diameter of a cylinder, which is assumed for the [Glu(OBzl)], helix, was found to be 17 A. The value (&,,)2/2yw, which is related to the ratio of weight-average permanent dipole moment fiw and electric polarizability anisotropy Aaw, was found to be in the range of 20-45. This indicates that the former contributes predominantly to electric field orientation, but the latter also should not be ignored. With the three parameters from the reverse portion, the rise and decay curves were regenerated theoretically in excellent agreement with experimental signals.

Reversing-pulse electric birefringence of nonconducting helical polypeptides in solutions: detection of the effect of applied electric field on polymer conformations from the relationship between the areas of buildup, reverse, and decay signals

“…is that the electric field orientation mechanism can be identified by inspecting a single RPEB signal with reference to theoretical predictions.28 Serious attempts were, however, made only recntly on the quantitative interpretation of experimentally observed RPEB signals to evaluate the electrooptical and hydrodynamic properties of nonconducting helical polypeptides in solution which are polydisperse regarding their lengths. [29][30][31][32][33] In this analysis, the feature of the reverse portion in RPEB signals, i.e., the extremum (a dip or a hump) and the time required to reach it, was utilized in the low-field region, together with the steady-state birefringence and the field-free relaxation time in the decay portion measured over a wide range of field strengths.…”

Reversing-Pulse Electric Birefringence of Poly(γ-benzyl L-glutamate) IV. Electric, Optical, and Hydrodynamic Properties in Helix-Forming Solvents as Evaluated from Field-On and Field-Off Processes

“…(/) is proportional to l, which is the case for the rodlike [Glu(OBzl)]n helix with the average length less than 1200 A. 24 The quantity <JJ. 2 )w or <JJ.>z<J.l.…”

Use of the Rotation Vector in Brownian Dynamics Simulation of Transient Electro‐Optical Properties

“…For rigid particles that are elongated in the direction of the axis of rotational symmetry, the analytical description of transient electrically induced birefringence is well known 1, 2. Our new BD‐algorithm can readily be used to simulate the dynamics of particle with arbitrary surface topography, but in order to have well established analytical solutions as references, here we only report on particles with axially symmetric surfaces.…”

“…[1,2] Our new BD-algorithm can readily be used to simulate the dynamics of particle with arbitrary surface topography, but in order to have well established analytical solutions as references, here we only report on particles with axially symmetric surfaces. When molecules with no surface symmetries are modeled as rigid bodies, the three Euler angles constitute the time-honored choice of generalized coordinates describing the molecule angular orientation.…”