Monte Carlo Simulation Study of Concentration Effects and Scattering Functions for Polyelectrolyte Wormlike Micelles

Abstract

We present an extensive Monte Carlo study on systems of many semiflexible chains with excluded volume and electrostatic interactions within the Debye−Hückel approximation. The model is tuned to mimic charged wormlike micelles in solution under different conditions. Simulations have been performed at different ionic strengths of added salt, charge densities, chain lengths, and volume fractions (η), covering the dilute to concentrated regime. The simple model used is able to reproduce the structural peak of the scattering function S(q), observed in many experiments, and other important features of polyelectrolytes in solution. Universal behavior of S(0) is established after a rescaling of η. Single-chain scattering functions, radii of gyration, and end-to-end distances have been sampled and compared with data from previous simulation studies and theories. The persistence length has also been analyzed and compared with the Odijk−Skolnick−Fixman predictions. The behavior of the quantities studied is in general found to be more complex than scaling theory predictions.

Salt-concentration dependence of the structure and form factors for the wormlike micelle made from a dual surfactant in aqueous solutions

“…We observe exactly the same behaviour as reported for polymer-electrolyte and salt free (or lowionic strength) wormlike micelle solutions (Sommer et al, 2002). Cannavacciuolo et al (2002) carried out a Monte Carlo simulation on systems consisting of many charged wormlike micelles with excluded volume and electrostatic interactions and concluded that the scattering function becomes almost identical with that of uncharged system when the ionic strength is more than 0.1 mol l À1 . This is because the electrostatic screening due to added salt is large enough to reduce repulsion between charged micelles.…”

“…On the other hand, for randomly oriented rodlike or wormlike micelles, the calculation becomes difficult. Recently, Cannavacciuolo et al (2002) presented an extensive Monte Carlo study on charged wormlike micelles to calculate S(q). To obtain P(q) from the observed data, I(q)/C D was extrapolated to the limit C D !…”

Regimes of electrostatic collapse of a highly charged polyelectrolyte in a poor solvent

“…We note that if all monomers of DNA were charged, one obtains B 29 and the range of these experimentally realizable B values are similar to the ones considered in this study. Another system with a comparably high linear charge densities is solution of charged worm-like micelles [47][48][49] . We hope that experimentalists find it interesting to check the existence of different collapse regimes for different counterion valencies and sizes.…”

Water‐in‐Oil Micro‐Emulsion Enhances the Secondary Structure of a Protein by Confinement

“…to the measured SAXS data for three concentrations c j for each q value q i ; P i , R int and a are fit parameters. The approach is similar to a classical Zimm analysis, except that it is expected to be applicable at higher concentrations in the full SAXS q range, since it has a more general form that can reproduce the behaviour found by PRISM theory and simulations for more strongly interacting systems 25. The fit to the data was performed using a standard nonlinear least‐squares method, and the standard error on the data extrapolated to zero concentration P i is directly obtained from the least‐squares analysis as the errors on the fit parameters.…”