multi- compartment micelles

One important target in the field of self-assembly of segmented copolymers (i.e. block, graft, star-block or miktoarm star copolymers) in solution is the design of new micellar morphologies with enhanced properties. The scope of conventional micelles either composed of low molecular weight surfactants or A-B segmented copolymers is inherently limited by the use of only one type of amphiphilic molecule generating only one type of micellar organisation in solution (i.e. hydrophilic shell and hydrophobic core). Thus, for drug-delivery applications, such structures only offer a single domain (the hydrophobic inner core) for drug entrapment. However, in Nature, some biological systems such as human serum albumin (HSA) are able to selectively uptake and release different substances at the same time. The concept of a "multicompartment micelle" is inspired by this singular behavior of HSA. Multicompartment micelles, possessing coexisting segregated inner-regions, could be capable to entrap several drugs of different types and deliver them simultaneously in the human body. Such structures can be prepared via the self-assembly in aqueous media of predesigned amphiphilic polymer architectures. The latter can be either linear (A-B-C triblock or A-B-C-B-A pentablock copolymers) or branched (graft terpolymers A-graft-B/C). However, in all cases, one key for the preparation of multicompartment micelles is the chemical nature and the length of the 3 polymer segments A, B and C. Segment A should be hydrophilic while B and C should be both hydrophobic and thermodynamically incompatible (for example B can be a hydrocarbon polymer chain and C a fluorocarbon chain). Such tailored architectures can be prepared by combining several synthetic methods: controlled radical polymerization, ring opening polymerization and coupling of telechelic polymers.

Possible morphologies for such multicompartment micelles could be diverse. A micro-phase separated core surrounded by a water-soluble spherical shell is expected. However, the core morphology could be of different types: onion-like (cf. scheme), spheres in sphere, lamellar... These complex micellar organisations are studied in our group by analytical ultra centrifugation, dynamic and static light scattering, small angle x-ray scattering, viscometry, electron microscopy and atomic force microscopy.