Size, flexibility, and scattering functions of semiflexible polyelectrolytes with excluded volume effects: Monte Carlo simulations and neutron scattering experiments

Abstract

We present a systematic Monte Carlo study of the scattering function S(q) of semiflexible polyelectrolytes at infinite dilution, in solutions with different concentrations of added salt. In the spirit of a theoretical description of polyelectrolytes in terms of the equivalent parameters, namely, persistence length and excluded volume interactions, we used a modified wormlike chain model, in which the monomers are represented by charged hard spheres placed at distance a. The electrostatic interactions are approximated by a Debye-Huckel potential. We show that the scattering function is quantitatively described by that of uncharged wormlike chains with excluded volume effects provided that an electrostatic contribution is added to the persistence length. In addition we have studied the expansion of the radius of gyration and of the end-to-end distance. The results are in agreement with the picture outlined in the Odijk-Skolnick-Fixman theory, in which the behavior of charged polymers is described only in terms of increasing local rigidity and excluded volume effects. Moreover, the Monte Carlo data are found to be in very good agreement with experimental scattering measurements with equilibrium polyelectrolytes, i.e., giant wormlike micelles formed in mixtures of nonionic and ionic surfactants in dilute aqueous solution, with added salt.

Wormlike micelles: where do we stand? Recent developments, linear rheology and scattering techniques

“…It has been shown that neglecting the interactions strongly affects the determination of micellar structural parameters, in particular the persistence length l p . 30,37,48,82,93,220,221 In the past few years, such structural models have been developed by Pedersen and Schurtenberger and co-workers, based on theory originally developed for polymers, combined with the results of Monte Carlo simulations, which now allow a full interpretation of the scattering data from long semiflexible micelles. 48,[220][221][222][223][224] For a recent review on the application of Monte Carlo techniques to obtain parameterized scattering functions for wormlike micelle systems, with and without electrostatic interactions, see ref.…”

Determination of the local density of polydisperse nanoparticle assemblies

“…Structure factors are calculated differently for the entire simulation box representing an "infinite" system, and finite subsets. By treating the entire simulation box as the unit cell of an infinite cubic lattice, finite-size effects are avoided: the structure factor of the "infinite" system can be calculated at the reciprocal lattice points of the box, i.e., at certain q-values qp defined below, and in certain directions compatible with the cubic lattice: [51][52][53][54][55]…”

Persistence length of polyelectrolytes with precisely located charges

“…Understanding the relationship between polyelectrolyte conformations, charged group distribution along the polymer backbone, and ionic strength is a complex problem that has been studied experimentally, theoretically, and in computer simulations. 3,[5][6][7][8][9][10][11][12][13][14] One of the most common measures of polyelectrolyte chain conformation is the persistence length. Persistence length impacts a wide range of polymer properties, such as intrinsic viscosity, 15 electrical conductivity, 16 and in concentrated solutions or in the bulk, ion clustering.…”