Control of structure and stability of vesicular systems by means of amphiphilic copolymers and their fixation

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Vesicles are very important colloidal systems, where the control of structure, properties and stability are of central importance for their potential applications. As they are often metastable systems, there is the option to manipulate vesicle properties by the presence of additives during the formation process and thereby to obtain kinetically controlled products. In this project we will in particular consider the effect of amphiphilic copolymers on spontaneously forming surfactant vesicles, with the aim of controlling structure and properties by the type and amount of added polymer and the subsequent fixation of these kinetically controlled systems. Pre-work on a model system has shown, that strongly synergistic surfactant mixtures form vesicles via a disk-like intermediate. Correspondingly this intermediate structure can be stabilized by the addition of a copolymer. By doing so the size and polydispersity of the vesicles can be controlled and these polymermodified vesicles are also much more stable against ageing processes. In this project these very interesting results regarding control of size, polydispersity and stability by means of amphiphilic copolymers shall become generalized and be put on a solid and broad basis. For this purposes surfactant mixtures relevant for applications will be investigated with respect to the effect of copolymer addition. . This will yield a comprehensive spectrum of relevant copolymer/surfactant mixtures for stable vesicle systems, where the copolymer functions here as a kind of 'colloidal catalyst', that modifies the pathway of vesicle formation. Due to the kinetic control this process yields very monodisperse systems, which are relatively long-lived due to the presence of the copolymer. This time window shall be used in order to chemically fix these well-defined structures and thereby create permanently stable structures. This shall be done in first by polymerization of organic monomers, and alternatively by using inorganic precursors, where by hydrolysis an inorganic framework is formed. Such fixed vesicle systems are not only interesting due to their long-time stability but also as e. g. their permeability and therefore the release of active agents can be controlled by type and extent of the fixation. The permeability and the mechanical properties of the fixed vesicles will become characterized, in order to be able to generate tailor-made properties of these permanent hollow nanostructures. In general, this project will produce in a controlled fashion vesicles and vesicle hybrid systems with desired properties and functionality, as they are of high interest for a variety of applications.