Poly(dimethyl phosphazene) displays, upon crystallization, a polymorphic behaviour showing two crystalline modifications, form I with a chain periodicity of 4.9/~, and a melting point of 146°C and form II with a chain periodicity of 5.85/~ and a melting point of 76°C. Form I, the only crystalline modification that is observed upon melting and recrystallization, has been completely characterized from a structural point of view through the study of X-ray diffraction patterns from oriented fibres and powder samples. A final structural refinement was carried out with the Rietveld method. The unit cell is monoclinic, space group P21/c and the cell parameters are a = 6.345(2), b = 13.805(4), c = 4.887(2)/~,//= 110.45(3) °.
Посилання на статтю:
The polymorphic behaviour and the crystal structure of one modification of poly (dimethylphosphazene / Stefano V. Meille and Anna R. Poletti // Polymer. – 1992. – Vol 33. – P. 2364-2369.