Libraries of minidendrons as maquettes for the exploration of the nanostructural diversity and complexity accessible from supramolecular dendrimers

Self-assemblies with well-defined shapes obtained from combinations of building blocks within complex architectures are the basis for the formation of natural structural and functional materials. Reversible self-assemblies of nucleic acids with proteins that have defined internal structure in solution, i.e. viruses, represent some of the best elucidated biological supramolecules. This thesis represents our latest efforts to synthesize structural, functional and systemic mimics of such natural complexes, using a strategy based on the molecular design, synthesis and characterization of non-biological dendritic supramolecular self-assemblies that resemble in a primitive way the assembly of cylindrical or icosahedral viruses.; Our investigation employed building blocks able to self-assemble into cylindrical or spherical supramolecules that afforded hexagonal columnar or cubic thermotropic lattices. Model dendrons, i.e. minidendrons , were used as maquettes for the elaboration of high generation dendrimers and we demonstrated their potential in determining: (a) critical structural parameters for the self-assembly, (b) thermally-induced shape change mechanism, (c) novel architectural motifs. In addition, covalent linkage of these maquettes via a poly(ethyleneimine) backbone allowed: (a) the elucidation of the shape change mechanism as a function of the degree of polymerization, (b) the demonstration of the structural quasi-equivalence of these dendrons in the self-assembled state and (c) visualization of the self-assemblies on surfaces. These findings afforded the possibility of the estimation of the structure-properties relationship in self-assemblies formed from larger generations of dendritic structures.; Subsequent investigations involved the living ring opening metathesis polymerization of 7-oxanorbornene monomers bearing bulky dendritic substituents. The shape of the resulted self-assembly was monitored and the shape change event during the polymerization of suitable monomers was elucidated by employing kinetic methods. Under certain conditions, extremely bulky and rigid substituents prevent the propagation past a critical degree of polymerization and the active chain end is encapsulated by the supramolecular aggregate. This results in a non-statistical interruption and the contained polymer chain is monodisperse. This synthetic system presents a sum of characteristics encountered before only in nature, i.e. molecular recognition directed synthesis, programmed control over the molecular weights, encoding of the final shape and size in the parental structure, and functionality preservation.