Single-coil properties and concentration effects forpolyelectrolyte-like wormlike micelles: a Monte Carlo study

Abstract

Results of an extensive Monte Carlo (MC) study on both single andmany semiflexible charged chains with excluded volume (EV) aresummarized. The model employed has been tailored to mimicwormlike micelles in solution. Simulations have been performedat different ionic strengths of added salt, charge densities,chain lengths and volume fractions Φ, covering the diluteto concentrated regime. At infinite dilution the scatteringfunctions can be fitted by the same fitting functions as foruncharged semiflexible chains with EV, providedthat an electrostatic contribution bel is added to thebare Kuhn length. The scaling of bel is found to be morecomplex than the Odijk-Skolnick-Fixman predictions, andqualitatively compatible with more recent variationalcalculations. Universality in the scaling of the radius ofgyration is found if all lengths are rescaled by the total Kuhnlength. At finite concentrations, the simple model used is ableto reproduce the structural peak in the scattering functionS(q) observed in many experiments, as well as otherproperties of polyelectrolytes (PELs) in solution. Universal behaviourof the forward scattering S(0) is established after arescaling of Φ. MC data are found to be in verygood agreement with experimental scattering measurements withequilibrium PELs, which are giant wormlikemicelles formed in mixtures of nonionic and ionic surfactants indilute aqueous solution, with added salt.