The preparation and properties of nano-sized blackberry-type structures are described. The capsules are composed of two types of block copolymer aggregates, a relatively large core vesicle, onto which is deposited a layer of smaller vesicles or micelles. The composition of the adjacent layers is such as to assure strong electrostatic interactions between them. The core vesicles can be composed of either PS-b-P4VP with a positively charged corona or of PS-b-PAA with a negatively charged corona, and can be surrounded by a layer of smaller, oppositely charged block copolymer vesicles or micelles. These composite structures bear a strong resemblance to blackberries, hence the proposed name. The blackberry structures can be prepared in solution or on a flat surface, e.g. a silicon wafer. Four compositional possibilities for the blackberries structures were studied, in which the positively or negatively charged core vesicles are covered either by a layer of oppositely charged micelles or vesicles. These structures represent the earliest stage of a layer-by-layer approach of small spherical aggregates onto a larger spherical hollow core. The strong interaction between the contacting layers is achieved by electrostatic interactions or by complementary acid-base properties, e.g. H-bonding. These multi-compartmented capsules are worth exploring as delivery vehicles for multiple components; each layer of the capsules could be loaded with hydrophobic (in the core of the micelles or vesicle wall) or hydrophilic molecules (in the vesicle cavity). The overall size of such structures can be kept below one μm.
adi.eisenberg@mcgill.ca
