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

Abstract

Recent molecular dynamics calculations6 suggest a picture consisting of a liquid-like hydrocarbon core surrounded by a slightly more ordered headgroup region. In order to confirm this picture, as well as to provide a general description of the effects of confining polymethylene sequences to a small spherical region, the authors present the results of Monte Carlo simulations of two simple models of a spherical micelle and of a n-alkane droplet of similar size. A tendency of the chain ends to concentrate near the interface is not unexpected, since the placement of internal units near the interface is intuitively associated with higher orientational and conformational constraints. In order to check this point, we have examined the order parameters smk, defined as (3/2) <cos2 θmk> - ( 1/2 ), θmk being the angle between the radius vector and the vector from unit k to unit k + m of each chain.