STRUCTURE OF POLYMER-LIKE MICELLES: SANS AND MONTE CARLO SIMULATION STUDIES. J.S. Pedersen, G. Jerke*, M. Laso*, and P. Schurtenberger*, Department of Solid State Physics, Risoe National Laboratory, DK-4000 Roskilde, Denmark; *Institut fuer Polymere, ETH Zuerich, CH-8092 Zuerich, Switzerland

Giant worm-like micelles behave essentially as semi-flexible polymers in a good solvent. This is most clearly reflected in the results of scattering experiments. The scattering function shows all the features of classical polymers. Depending on the scattering vector region, one can extract information on overall size, flexibility and the cylindrical cross-section structure. However, as the micelles are self-assembling equilibrium structures, they have a large size polydispersity. The systems studied in the present work is lecithin in deuterated isooctane or cyclohexane with trace amounts of water. Detailed information on cross-section structure of the micelles has been obtained by SANS and contrast variation using heavy water. The structure was determined model-independently using the indirect Fourier transformation and square-root deconvolution techniques. In order to perform an accurate modeling of the scattering data in the full range of scattering vectors, we have performed and extensive Monte Carlo simulation study of a Kratky-Porod-type model for semi-flexible polymer chains with excluded volume effects. The scattering functions were determined and parameterized, so that they can be used for fitting the data. The fitting of the experimental data provides information on the size distribution and persistence length. The latter describes the local flexibility of the micelles. For the isooctane system the persistence length shows a pronounced concentration dependence with a value of 150 A in the dilute limit. The concentration dependence reflects the inter-micellar interaction effects in the semi-dilute regime. Our recent Monte Carlo simulations on many chain systems confirm this conclusion.