Molecular arrangements and conformations of the alkyl chains in spherical micelles and droplets

Abstract

We have modeled two systems of spherical micelles and of n-alkane droplets, each consisting of 52 molecules comprised by 13 units each in a spherical region of approximately 1.6 nm radius, by the Monte Carlo simulation method. The simulated model micelle exhibits the distribution of chain segments in good agreement with the results of neutron scattering and NMR experiments on micelles having similar compositions. Both the micelle and the droplet models show that the segments in the interior of the chains tend to stay away from the interfaces, resulting in enhanced chain-end densities at the surface region. Moreover, chain segments in contact with the interface tend to orient along the interface, thus exhibiting negative order parameters with respect to the radius vector. Despite this local anisotropic orientation, however, the average conformation of the alkyl groups is only slightly different from that of the unperturbed random-coil model. © 1990 American Institute of Physics.