Effect of spatial restrictions at the nanometer scale on structuring in glassy and crystalline polymers

The literature data on the effect of nanometer-scale spatial restrictions on the phase transitions and crystallizability of polymers are analyzed. It is shown that, as the volume of the polymer phase is decreased and its linear sizes take values on the order of 50 nm or less, the fundamental properties of the polymers change abruptly. The glass-transition temperature may decrease by tens of degrees, the temperature and heat of crystallization and the temperature and heat of melting may decline sharply, and the degree of crystallinity of polymers may become lower. Shredding of the polymer into nanometer sizes strongly affects the type of nucleation during its crystallization. As the length of the polymer phase is decreased, the transition from heterogeneous nucleation, which is usually observed during crystallization of bulky polymers, to homogeneous nucleation occurs through the stage of fractional crystallization. The crystallization of polymers under confined conditions is accompanied by the orientation of crystallites in the nanometer asymmetric space and is controlled by the size and morphology of restriction, the character of its interaction with the solid surface, and the ratio of the rates of nucleation and growth of crystals. The analyzed data are of great importance in the manufacture of such miniature objects as nanorods and nanowires necessary for the development and creation of modern devices used to solve important applied problems in microelectronics and biomedicine. The mentioned spatial effects should be taken into account during the creation of nanostructured films for solar cells and polymer membranes of energy separators, for the targeted delivery of drugs, and in many other fields.