Mean-field models of size selection in polymer vesicles with and without interdigitation

Abstract

ABSTRACT Block copolymers in solution can form vesicles with a preferred size when the degree of polymerisation of the hydrophobic block is significantly greater than that of the hydrophilic block. In an earlier publication, we introduced a mean-field theory that treats the vesicle membrane as a bilayer. Here, a model is presented in which the hydrophobic blocks form a single interdigitated layer. In the model with interdigitation, the vesicles still have a preferred radius, but this increases more slowly as a function of than in the bilayer model, in better agreement with experiment. However, the predictions of the bilayer model for the relationship between and the vesicle membrane thickness are consistent with the experimental result over a wide range of parameters, while the model with interdigitation predicts an exponent of around . This suggests that the structure of the vesicles may lie between these two cases.