The kinetics of the structural first order phase transition in the tetracosane С24Н50 monodisperse samples is studied with the help of FTIR spectroscopy. The temperature dependencies of the frequency and intensity of rocking (ν~ 720 cm-1) and bending (ν~ 1470 cm-1) vibrations of СН2-groupes in the methylene trans-sequences in the crystalline cores of the elementary lamellae are investigated. It is shown that the first order solid phase transition is developing on a heterogeneous mechanism in the narrow temperature interval (T~ 2 K) according to the theory of the diffused first order phase transitions and is due to the crystalline cell symmetry change.
The kinetics of the development of a diffuse phase transition of the first kind in monodisperse samples of tetracosan C24H50 was studied by FT-IR spectroscopy.The temperature dependences of the frequencies and intensities of C-H stretching vibrations in the spectral region ν=2800-3000 cm-1 were studied for 4 different modes in the methylene CH2 trans sequences of the main chain and for 4 different modes corresponding to the end methyl CH3 groups. Specific changes in the vibrational frequencies of all investigated modes are found, which are caused by changes in the symmetry of the packing of molecules during a phase transition of the first order.
A method is proposed for calculating the dimension distribution of nanocrystalline elements of the lamellar and fibrillar morphologies of a polymer. Calorimetric data were used to calculate the distribution of the longitudinal size of these elements in lamellae and microfibrils of ultrahigh molecular weight polyethylene. The calculation results are consistent with the data obtained by the X-ray method.
V. M. Egorov1, A. K. Borisov1, V. A. Marikhin1, L. P. Myasnikova1, S. A. Gureva1, E. M. Ivan’kova2
1 Ioffe Institute, 26 Polytechnicheskaya, St. Petersburg 194021, Russia
2 Institute of Macromolecular Compounds, 31 Bolshoy pr., St. Petersburg 199004, Russia
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