Abstract

In material science, the possibility of creating chemical or physical patterns on various materials has opened a wide range of possibilities. Several techniques are available for patterning; among these, self assembled structures raised great interest. Changing the environmental humidity during solvent evaporation from a cast polymer solution, the condensation of water droplets is promoted, which self-assembled in a regular array; these drops form a template for the formation of an array of pores on the film, called Breath Figures. A similar mechanism seems to happen not only during film casting, but also during the formation of fibers in the electrospinning process. This work is focused on the understanding of the mechanisms involved in pores formation due to the interaction of polymeric solution surface with humidity. The process parameters were controlled to tune the pores arrays features, according to the purpose they are used for. Moreover, the interface between the polymeric surface and the water droplets was exploited to promote the migration of hydrophilic chemical groups, obtaining the chemical functionalization of the inner surfaces of pores. In this way, a topographical and chemical pattern was obtained on the film surface. The formation of pores was studied on the surfaces of flat films and on electrospun fibers; both structures were developed for two main applications: drug release and interactions with cells. Porous films were demonstrated to release proteins in a controlled manner, depending on pores features and on chemical patterning. In particular, the release of protein with high molecular weight was developed. Films were demonstrated to influence cells adhesion depending on pores dimension and distribution. Pores on the surface of fibers where demonstrated to influence the release of drugs from mats produced by coaxial electrospinning. Similarly to films, electrospun fibers were studied to understand their ability to influence cells behavior. The final aim is the production of patches for drug release and of scaffolds that combine the ability to support tissue growth and the release of therapeutic molecules.