EXPLORING THE PHYSICS OF POLYMERS AND LIVING POLYMERS THROUGH DNA MODELS

In the last twenty years DNA has become a topic of research in material science and technology. It was in fact realized that the code depending pairing of DNA polymers could be exploited to program their self assembly into complex multi-strand structures. This field of research, which is generally named DNA structure of nanotechnology, has been constantly growing. While at its origin the products of DNA assembly where simple geometrical shapes the latest achievements involve quite sophisticated programmable structures, including mobile nano-spiders, fueled by DNA. The general philosophy underlying this effort is to try to master DNA properties to obtain complex nano-structures by spontaneous self-assembly. The aim of this field is, in principle, technological. In parallel to this enormous development of DNA nanotechnology, a distinct branch of material science research has emerged in which the properties of DNA are exploited, namely the use of DNA structures as a molecular model capable of setting the stage to explore relevant processes of condensed matter physics. Among these the use of DNA to explore the physics behind the formation of LC phases, and the use of DNA aggregates as a model of low valence molecules. The class of problems considered in this thesis involves both polymer physics and liquid crystal formation. The latter is also intimately related to polymerization in that the formation of LC phases in short DNA oligomers is mediated by their aggregation into living polymers. Indeed, polymerization and LC formation, besides sharing a basic uniaxial symmetry, might be even more intimately connected as the formation of LC ordering might even be the cradle for the development of long polymeric chains obtained by the chemical stabilization of living polymers.