Barbiturate dyes containing either a dipolar or polarizable chromophoric system have been synthesized and their solvatochromism investigated. The effect of specific and non-specific solvent interactions on the position of their UV/Vis absorption bands has been evaluated by using the Kamlet-Taft

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The research topics of our group are in general from the field of physical chemistry of colloidal systems. Within this rather wide layout a large variety of quite different questions and systems are tackled, where the common bridging factor is the aim of understanding the properties of colloidal systems based on their mesoscopic structure and dynamics, which in turn are controlled by their molecular composition. With such an enhanced understanding of the correlation between mesoscopic structure and the macroscopic properties the goal then is to employ this knowledge in order to formulate increasingly complex colloidal system with correspondingly more variable and interesting functionalities. From this general context of investigations, some representative systems and questions that have been studied in recent time by us are covered in this text.They comprise the phase behaviour and the structures formed in solutions of surfactants and amphiphilic copolymers. Once these static properties are known, we also have a high interest in the dynamic properties and the kinetics of morphological transitions as they are observed under non-equilibrium conditions, since they are frequently encountered in applications. A key property of amphiphilic molecules is their ability to solubilise sparingly soluble compounds thereby forming microemulsions or nanoemulsions, where the ability to form such systems depends strongly on the molecular architecture of the amphiphiles. By turning to polymeric amphiphiles the concept of surfactants and their architecture can be extended largely towards more versatile structures, more complex self-assembly and much larger length and time scales. Another direction is the surfactant assisted formation of nanoparticles or mesoporous inorganic materials. By combining copolymers with other polymers, copolymers, colloids, or surfactants – for instance via electrostatically driven co-assembly – one may then form increasingly complex colloidal aggregates. By doing so one is able to control rheological properties or develop complex delivery systems, whose properties can be tailor-made by appropriate choice of the molecular build-up. This striving towards well controlled complexity achieved by means of self- and co-assembly then leads to increasingly more functional systems and is the key direction for future research activities in our group.

Phase behaviour and static structure of surfactant systems have been studied in much detail, but this applies much less so to their dynamic properties. Structural transitions in amphiphilic systems can be triggered by mixing different amphiphiles. Employing the stopped-flow technique we have studied the kinetics of formation of multilamellar vesicles starting from a micellar solution and a microemulsion containing a semipolar oil. This process has been investigated for various starting conditions and as a function of the charging of the amphiphilic system. The formation process is the faster the closer the starting solution is in composition to the final state and can be slowed down by the presence of ionic surfactant.