ИСТИНА

Supercritical carbon dioxide (sc CO2) may dissolve some polymer materials. Polymer solution in sc media demonstrates rather unusual properties. Due to peculiar nature of sc fluid it may penetrate deep into any open pores even the tiniest ones without encountering any resistance from capillary forces—these forces just absent for sc fluid in a capillary. Therefore, polymer solution in sc solvent is characterized by absolute wetting ability for surfaces and absolute permeability for porous media. This feature opens new options for delivery functional polymer materials inside different porous matrixes when the sc CO2 under high pressure and elevated temperatures serves as a carrier. During decompression step the solvent (sc CO2) leaves the matrix completely, again without any influence of capillary forces. Thus, the delivered functional polymer material remains to be distributed on a surface of pores of the matrix as an undisturbed ultrathin film with nanometer-scale thickness. Yet, general features of material deposition on a substrate surface from solutions in sc CO2 are not completely understood. Therefore, we are performing systematic studies of the morphology of deposited nano-structures from such solutions on a model substrate. As far as we used mainly scanning force microscopy (SPM) as a tool to analyze the morphology with nanometer-scale spatial resolution it is necessary to select atomically flat model substrates such as mica or highly oriented pyrolytic graphite. In that case SPM provides direct information on the organization of polymer materials on a substrate. This approach will be demonstrated on the examples of ultrathin films or nanostructures of fluoropolymers, dendrimers, chitosan derivatives, organometallic complexes, etc. as deposited directly from solutions in sc CO2. Further development of this technology may result in production of composites with advanced properties to be applied in fuel cells, biomedical applications and membrane systems.