Multimicelle aggregate mechanism for spherical multimolecular micelles: from theories, characteristics and properties to applications

Abstract

Spherical micelles are the most commonly and widely used supramolecular structures in the self-assembly studies of amphiphilic polymers and for applications in areas such as sensing, drug delivery, diagnostic and functional materials. According to their structure and size, spherical micelles can be classified as small simple micelles (with size less than 30 nm) and large complex micelles (with size more than 30–50 nm); the formation of small simple micelles can generally be explained by a “star micelle” mechanism; however, this mechanism cannot be used to explain the formation of large complex micelles. Currently, the mechanisms to explain the formation of large complex micelles include “large compound micelle”, “multicompartment micelle”, “supermicelle” and “multimicelle aggregate” (MMA) mechanisms. The MMA mechanism can be divided into unimolecular micelle aggregate (UMA) and small micelle aggregate (SMA) mechanisms and is quite different from other mechanisms in terms of the structure and property of micelles; in addition, although MMA was proposed to explain the formation of large multimolecular micelles from hyperbranched polymers at the beginning, to date, it has been proved to be applicable for explaining the formation of large micelles from other amphiphilic polymers such as dendrimers, comb polymers, graft polymers, star polymers, linear polymers and even small molecules. Furthermore, due to their special structure, MMAs have shown unique potential applications in light-emitting materials, light-harvesting systems, nanoporous materials and biomedical areas; in this review, we have summarized the recent progress in the mechanism, precursors, structural characteristics and properties of MMAs as well as their applications.