Nanocapsules containing the hydrophilic contrast agents Magnevist® and Gadovist® are synthesized in an inverse miniemulsion process. First, nanodroplets of 100 to 550 nm are formed which are subsequently encapsulated by an interfacial polyaddition in polymeric shells of polyurethane, polyurea and crosslinked dextran. The shell thickness can be adjusted by the monomer concentration. Due to the porosity of the polymeric shell, exchange of water molecules through the capsule wall can be ensured and no significant compromises in the T1 relaxitivity of the contrast compound is observed for magnetic resonance imaging (MRI). This clearly indicates the potential use of the contrast agent filled nanocapsules as new MRI contrast agents.magnified image

A statistical library of well-defined ionic and non-ionic amphiphilic block copolymers of P(MMA/ HEMA)-b-PDMAEMA and PEG-b-P(MMA/HEMA) were synthesised via living radical polymerisation employing the macroinitiator technique. All the block copolymers show monomodal peaks and narrow weight distributions, indicating they were obtained in controlled manner. Those copolymers were further modified in order to prepare inisurfs and surfmers. This yielded a selection of active surfactants of desired molecular weight and low polydispersity. Soap-free miniemulsion polymerisations of butyl methacrylate were carried out using the obtained active surfactants to prepare core-shell microcapsules in which various concentrations of inert oil, hexadecane, as a model system were encapsulated. The influence of the block copolymer structure on the particle formation was studied. The core-shell nature of the particles could be confirmed using scanning electron microscopy. Up to 66% of hexadecane could be incorporated in PBMA microcapsules.

Polymer/complex hybrid nanostructures were prepared using a variety of hydrophobic metal β-diketonato complexes. The mechanism of structure formation was investigated by electron paramagnetic resonance (EPR) spectroscopy and small-angle X-ray scattering (SAXS) in the liquid phase. Structure formation is attributed to an interaction between free coordination sites of metal β-diketonato complexes and coordinating anionic surfactants. Lamellar structures are already present in the miniemulsion. By subsequent polymerization the lamellae can be embedded in a great variety of different polymeric matrices. The morphology of the lamellar structures, as elucidated by transmission electron microscopy (TEM), can be controlled by the choice of anionic surfactant. Using sodium alkylsulfates and sodium dodecylphosphate, "nano-onions" are formed, while sodium carboxylates lead to "kebab-like" structures. The composition of the hybrid nanostructures can be described as bilayer lamellae, embedded in a polymeric matrix. The metal complexes are separated by surfactant molecules which are arranged tail-to-tail; by increasing the carbon chain length of the surfactant the layer distance of the structured nanomaterial can be adjusted between 2 and 5 nm.