CRYSTALLINE TRANSITIONS AND RELATED PHYSICAL-PROPERTIES OF POLY(DICHLOROPHOSPHAZENE)

Highly purified, uncross-linked poly(dichlorophosphazene), (NPCl2)n (II), has been examined by X-ray diffraction, optical, differential scanning calorimetry, and dynamic mechanical techniques. The unstressed polymer is amorphous at 25 °C. Crystallization can be induced by cooling the polymer to -7.2 to -12 °C or by stretching of the polymer at 25 °C. Three different crystalline modifications were detected: lie, crystalline by cooling; IIs, crystalline by stretching; and Ilsr, a metastable crystalline form obtained from the stretched and relaxed polymer. The degree of crystallinity of IIs was 20% and that of Ilsr was calculated to be 11 %. The main crystal melting temperature occurred at +33.1 °C (IIc) or +39 °C (IIs), although the crystallization temperature on cooling is near -7.2 °C. However, additional endothermic transitions were detected at +12 and +25.4 °C for Ilsr. The values detected by use of the dynamic mechanical method differed from those found from X-ray diffraction or differential scanning calorimetry experiments. This anomaly is almost certainly a consequence of the sensitivity of the crystallization behavior of this polymer to stress effects. The physical properties of (NPCl2)n appear to be directly related to the inherent high flexibility of the chain. © 1979, American Chemical Society. All rights reserved.