Phd contract in the field of Chemistry financed for three years by the University of Clermont Auvergne

Study of supramolecular assemblies in homogeneous and heterogeneous phases

For various applications, including the development of "intelligent" materials and biosensors, thin films made of monolayers organized on surfaces are developed. Adsorbates then attach themselves to a solid surface (adsorbent) by various processes that may involve different types of bonds (physisorption or chemisorption). The formation of inclusion complexes on a surface by supramolecular chemistry allows the immobilization of many molecules on surfaces. The most commonly used host or receptor molecules are macrocycles modified by the introduction of thiol groups. They can then be assembled on a gold surface to form a monolayer. We have recently focused on the thermodynamics of supramolecular structures immobilized on a surface. By calculatingusing molecular simulation techniques, the free energy profile along the reaction coordinates between host and guest during the association process, thermodynamic association quantities can be obtained in the heterogeneous phase (the host and/or guest are grafted onto a surface) and compared with those obtained in the homogeneous phase (species are free in solution). This heterogeneous systems simulation methodology has recently been usedon model systems (the inclusion complexes of b-cyclodextrine and calixarenesulfonate and 4-aminoazobenzene) for which we were able to explain the differences between the homogeneous and heterogeneous phase association. This study has allowed a better understanding of the association process in the particular case of the inclusion of 4-aminoazobenzene.In order to complete this study and rationalize these self-assemblage processes, we aim to study the grafting cucurbiturils on different types of surfaces, in order to compare the affinities and selectivity of the different hydrophobic cages in the heterogeneous phase. Indeed, in the homogeneous phase cucurbiturils associate better than cyclodextrins and calixarenes. We will study this trendin the heterogeneous phase. The effect of the nature of the surface will also be examined. Thus, carbon nanotubes with their exceptional electrical, mechanical and thermal properties offer many applications in the field of biosensors. Different types of covalent or non-covalent functionalization based on compound adsorption are possible to allow protein anchoring.