| Abstract: | Detailed structure analysis of the polyoxymethylene molecule was carried out by the method of three-dimensional Fourier synthesis. The diffraction data were measured on a highly ordered polyoxymethylene sample prepared from a single crystal of tetraoxane by solid-state radiation polymerization. By assuming the anisotropic thermal factors for the oxygen and carbon atoms and taking into account the contribution of the hydrogen atoms, good agreement between the observed and calculated structure factors was obtained; the R factor is 8.8%. The distance between the oxygen atom and the helix axis r(O) = 0.671 A. is slightly shorter than r(C) = 0.691 A. The bond distance C? O = 1.421 A., the angle ∠COC = 112°24′, and ∠OCO = 110°49′. All the internal rotation angles of the skeletal bonds are 78°13′. It is deduced from the experimental results that each crystallite of polyoxymethylene is composed of only one type of helix, right-handed or left-handed. |
