ON THE SHAPE AND RHEOLOGY OF LINEAR MICELLES IN DILUTE-SOLUTIONS

We calculate steady state properties of linear (wormlike) micelles mod eled as flexible bead-spring chains from both microscopic and mesoscop ic models. The latter model is based on an expression for the free ene rgy of Gaussian chains, modified by a term which takes into account a finite scission energy in order to describe micelles, or breakable pol ymer chains. In equilibrium, the length distribution then depends on t wo parameters, namely the micellar concentration and the scission ener gy. Results of this approach are compared both with previous mesoscopi c descriptions and Molecular Dynamics (MD) computer simulation results of the FENE-C model of linear micellar solutions (Phys. Rev. E 53 (19 95) 2531). The mesoscopic model is extended to describe flow situation s. Implications are discussed and compared with NonEquilibrium MD (NEM D) computer simulation results for the length distribution and flow al ignment of linear micelles as well as the corresponding rheological be havior. For the case of steady shear flow both models do predict a dec rease of the average micellar size with increasing shear rate.