X-ray diffraction phase analysis of the crystalline phase of polytetrafluoroethylene
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URE OF ORGANIC COMPOUNDS
XRay Diffraction Phase Analysis of the Crystalline Phase of Polytetrafluoroethylene Yu. A. Lebedeva, Yu. M. Koroleva, A. V. Rebrova, L. N. Ignat’evab, and E. M. Antipova a
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskiі pr. 29, Moscow, 119991 Russia email: [email protected] b Institute of Chemistry, Far East Division, Russian Academy of Sciences, pr. 100Letiya Vladivostoka 159, Vladivostok, 690002 Russia Received August 19, 2009
Abstract—Samples of ultradispersed polytetrafluoroethylene, which were prepared with the use of different technological approaches, were studied by Xray diffraction. The samples were found to belong to the mon oclinic system. For some samples, basal reflections, which can be related to paraffins, were found for the first time. This indicates that polymer chains can form yet another type of monoclinic structure. DOI: 10.1134/S1063774510040139
INTRODUCTION
EXPERIMENTAL
In the last two to three decades, against common knowledge, flexiblechain systems whose macromole cules lack mesogenic groups have been found to exhibit mesophases containing 1D and 2D elements with a longrange positional order characterized by the orientational order and the conformational disor der. Such mesomorphic structures, called condis crys tals (B. Wunderlich) or columnar mesophases (G. Ungar), were observed for several classes of flexi blechain highmolecularweight compounds, such as polyorganosiloxanes, polyorganophosphazenes, poly carbosilanes, and polygermanes, some polydienes, polyesters, etc. [1–3].
The Xray diffraction measurements were carried out on automated DRON2.0 (measurements in the reflection mode using a modified collimation system) and DRON3M (measurements in the transmission mode using a nickel filter for the incident beam) dif fractometers using filtered CuKα radiation. The mea surements were performed in the 2θangle range from 1° to 80°. To detect weak reflections, the spectra were recorded in steps with long acquisition times. The alignment of the goniometer was periodically checked by recording the data for the standards (quartz and NaCl in the measurements in the reflection mode and a pentaerythritol single crystal in the measurements in the transmission mode). Three Xray diffraction pat terns measured for each sample were statistically pro cessed with the use of the Microcal Origin 6.0 program to determine the average interplanar spacings dhkl and were then indexed with the use of the Powtool pro gram. The Xray diffraction studies were also carried out on a Rigaku Rotaflex R200 Xray system (Japan) with variable geometry equipped with a 12kW rotating anode Xray generator (CuKα radiation, an incident beam graphite monochromator). A Bruker AG posi tionsensitive area detector (Germany) was used as the recording system. The degree of crystallinity of the samples was deter mined as the ratio of the integrated intensity of the crystalline peak to the overall intensity of this peak and the diffuse scatt
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