Molecular modeling study concerning the self-assembly capacity of some photosensitive amphiphilic polysiloxanes

Abstract

The understanding of self-assembly conditions has become the main purpose of experimental and theoretical research studies on micelles. Association of the micelles in clusters is a challenging topic, given the enhanced complexity of cluster systems. This work reports molecular dynamics studies on micellar structures of azo-polysiloxanes modified with quaternary ammonium groups like triethylammonium or dimethyldodecilammonium chloride. Previously, our experimental results have shown a very particular type of aggregation of long hydrocarbon chain amine-based micelles, which was not yet mentioned in the literature. If tertiary amines are low size, such as triethylammonium, the aggregation process of micelles in clusters is no longer present. Molecular dynamics simulations revealed the formation of an amphiphilic layer mainly composed of hydrocarbon chains of the ammonium groups, together with chlorobenzyl and azobenzene moieties. This ordering manner opposes to the idea of a continuous electrical layer of low molecular weight molecules on the surface of the micelle, or to those of a compositionally uniform coating formed by copolymers (diblock, triblock or graft). The herein paper also reports force field parameters, such as quantum mechanical derived atomic partial charges for the studied compounds, bringing improvements to the force fields developed so far.