USING AN X–RAY INTERFEROMETER TO DETERMINE SOME PARAMETERS OF POLYMERIC SUBSTANCES

Abstract

Among the main characteristics that determine the supramolecular organization of polymers, an important role is played by such parameters as the unit cell volume of crystallites and the Loschmidt number for a given substance, the knowledge of which will make it possible to draw certain conclusions about the arrangement of polymer chains in the supramolecular organization of polymers. It is also known that one of the important characteristics of substances in general, and for polymers, in particular, is density, the knowledge of which gives a certain idea of the structure of polymers, which largely determines their physical properties. The determination of these parameters is carried out by a number of methods with a certain degree of accuracy. For example, the parameters of a crystal cell, and hence its volume, are determined by the method of X–ray diffraction analysis – by obtaining the lattice periods in three main directions. However, the further decoding of the obtained radiographs is also associated with time–consuming operations. Moreover, the aforementioned X–ray method for a sufficiently accurate determination of the cell volume is used only for single crystals. To determine the volume of the unit cell of polycrystalline and polymerie substances by this method more accurately than it is done by other existing methods is completely impossible. The X–ray interferometric method proposed by us allows one to determine any of the above parameters for any substances with a single X–ray diffraction pattern.

A new X–ray interferometric method for determining the density, volume of a unit cell and Loschmidt number for some high–molecular compounds with the help of changing some moire patterns is proposed. It is shown that this method is equally applicable for polycrystalline and monocrystalline substances, as well as for inorganic, organic and high– molecular compounds. The above–mentioned characteristics are calculated for three standard polymers – polymethylmethacrylate, polystyrene and polychloroprene. To confirm the validity, our experimental results were compared with the literary data.