Geidarov V. Structural changes in polyimide PMA films under the action of deep cooling, annealing and low-temperature deformation

The dissertation work presents the results of X-ray structural studies of polyimide films obtained by various methods and with different thicknesses. It has been experimentally shown by X-ray diffractometry that deformation and cooling of a polyimide PMA film with a thickness of 80 μm have a different effect on the intensity distribution. So, as a result of deformation in the sample, areas of "tension" appear, and upon cooling, areas of "compression". Analysis of the diffraction patterns allows us to conclude that uniaxial tension of the samples leads to a partial ordering of polyimide molecules in the sample in the direction of the applied load. The observed change in the structure upon cooling the films may indicate that there is a mutual ordering of some of the molecules relative to each other. It is shown that the effect of temperature (annealing) leads to a smearing of a wide peak and an increase in the background intensity. This suggests that cardinal changes occur in the film associated with the geometry of the macromolecule. The findings of the study were that stretching polymer films with a thickness of 75 μm does not cause cardinal changes in the structure. The deformation of polymer films by thickness of 125 μm leads to the appearance of regions with long-range order in the sample.