Macromolecular Hyperarchitectures Obtained by Photo Cross-Linking of Self-Assembled Systems – HYPARC

Complex macromolecular architectures are not current and difficult to obtain in a controlled fashion by classical polymerization techniques. Difficulties for obtaining well defined structures slow down the development of researches which could lead, through the analysis of the physicochemical properties of such structures, to potential applications of these new materials. The aim of this project is to develop an original methodology for elaborating, in a controlled manner, macromolecular hyperarchitectures such as multi-arm stars, pom-pom, flower-like polymers, garland-like polymers down to nano-objects like nano-rods... The synthesis strategy is based on self-assembly properties of amphiphilic block copolymers in aqueous medium which lead, under specific conditions, to the formation of such structures with a transient or living state. The system has now to be rapidly frozen to reach our goals. For this purpose, we'll synthesize poly(ethylene oxide)(PEO)-b-poly(alkyl acrylate)(PA) block copolymers bearing polymerizable groups at hydrophobic chain-end. These copolymers form, in aqueous solution, micellar structures that will be fixed by photo crosslinking of micellar cores under UV light. The use of diblock copolymers leads to the formation of "model" multi-arm stars that will allow the validation of characteristics of micelles and the crosslinking conditions. The utilization of PA-PEO-PA tribloc copolymers bearing photo-polymerizable moieties or diblock / triblock copolymer mixtures will allow the elaboration of more original structures through bridges between micelles. The design of structures obtained after photo-crosslinking will be controlled through the physicochemical parameters that govern micellization (HLB, concentration, temperature, solvent quality). We will seek to obtain significant quantities of nanomaterials to allow an extensive study of their their properties. The analysis of hyperarchitecture physicochemical properties by size exclusion chromatography, static and dynamical light scattering and rheometry (in solution and in the bulk) will bring new results on the behavior of macromolecular complex structures. The ability to fix triblock copolymers forming aggregates (or gels), in their equilibrium or metastable state, will also allow a better comprehension of reversible aggregation and gelification processes. We'll be able to dilute aggregates and analyze them without any modification induced by the reversibility of the system. The hydrogels of tunable porosity could be applied as stationary phases in capillary liquid chromatography.