Birefringence, Deformation, and Scattering of Wormlike Macromolecules under an External Agent. Steady-State Properties in an Electric Field

Abstract

In this paper, we study the steady-state birefringence, deformation, and scattering of wormlike macromolecules under the influence of an electric field. We use a model of N + 1 pointlike elements whose connectors define N axially symmetric subunits. The model is able to describe some properties of segmentally flexible and wormlike macromolecules depending on the choice of N. We use the Monte Carlo computer simulation technique to characterize the effect of the electric field on the orientation and deformation of molecules with permanent and induced dipoles. Using this technique, we study the effect of the field in different models with the same flexibility (defined as 〈s2〉0/〈s2〉0,str). Orientation is studied through changes in birefringence and deformation through changes in the gyration tensor of the molecule. When the behavior of a broken rod (typical case of segmental flexibility) and a wormlike chain is compared, the differences are generally quantitative although significant enough to be used to obtain information about the internal structure of a macromolecule.

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: A computer simulation study

“…For flexible models made up of beads connected by virtual bonds, the usual ap-proximation is to assume that associated with each virtual bond is an electric polarizability tensor, which is axially symmetric about the bond vector. [20][21][22][23] As a summary, the orientation mechanism of flexible macroions is complex and the pairwise additive models may be as good as we can do at the present time. This model of orienting mechanism has been named sometimes as "pairwise additive."…”

“…As argued in a previous work, 23 there are different ways of defining the flexibility of a wormlike molecule. ͑2͒, P is the persistence length and L is the contour length.…”

“…22,23 Of course, the magnitude of such deformation is directly related with the orienting mechanism, the intensity of the field and the type and degree of flexibility. We have addressed this question because in a TEB experiment, a flexible molecule is deformed by an electric field of any intensity.…”

“…20,21,25,23 Here, we summarize a few essential features. The mechanical, hydrodynamic, and electro-optical description of the model is as described in earlier papers.…”

Solution Properties of Flexible Macromolecules: Theoretical and Computational Approaches

“…These theories made some simplifying assumptions about hydrodynamic interactions, but it seems that a set of characteristic relaxation times really exists for every flexible molecule; indeed, it has been shown that τ 1 is the same regardless of the property or technique used in its measurement. 10,11 All these considerations illustrate the complexity of describing the full dynamics (simultaneously translational, internal, etc.) of flexible macromolecules.…”