Title of the thesis: Study of supramolecular assemblies in homogeneous and heterogeneous phases
Supervisor : A. Ghoufi, C. Bonal et P. Malfreyt
Laboratory : ICCF
University : UCA
Email and Phone : [email protected] , 04 73 40 71 65
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 calculating mean force potentials between entities 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 used on 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.
These simulations will be completed by also studying the possibility of grafting cucurbiturils on 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 trend in 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.
Finally, we propose to focus on these systems using a multi-scale approach. Indeed, for various applications in biomedicine or biotechnology, it is necessary to immobilize biomolecules such as proteins, enzymes, DNA on surfaces. To study these complex "biomaterials" type systems, a new simulation methodology will be developed. Indeed, their sizes require the use of "coarse-grained" descriptions with spheres that interact with each other by a potential of the MARTINI type.
All the simulations carried out in this thesis will aim to better understand the behaviours and interactions of molecules at the interfaces, the site of heterogeneity and anisotropy in interactions.
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