A Study for the Mesomorphic State of Polyorganophosphazene in Terms of Time-sharing X-ray Diffraction

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Crystallizable polyorganophosphazenes (POP) have so-called T(1) transitions at which the polymers change from their 3-D ordered crystalline state to the 3-D ordered mesomorphic structure ( e.g., the delta phase ). The transition is generally known to locate between the glass transition temperature and the true melting point of POP.In this research, structural studies for crystallization processes from the delta phases associated with two types of polyphosphazenes have been carried out by a time-sharing x-ray diffraction method, and the findings were compared with the thermal properties of those POP examined. The results obtained are summarized as follows :(1) When the poly[bis(4-ethylphenoxy)phosphazene] (PB(4E)PP) films heated at 140ﾟC were cooled down rapidly to an isothermal temperature of 75ﾟC, the mesomorphic states of the polymer remained without crystallization. This freezing of the meso state was confirmed by the x-ray experiments with PSPC.(2) The thermogram for the PB(4E)PP film obtained by a rapid cooling rate of 300 K/mm did not indicate any exothermic behavior, as agreed with the structural features above observed.(3) Morphological features of freezed PB(4E)PP were also investigated by use of a cryo SEM.(4) We examined the crystallization behavior of the delta phase of poly(bis(3,4-dimethylphenoxy)- phosphazene] (PB(dM)PP) in a similar manner using time-sharing x-ray diffraction and DSC, and succeeded in freezing its meso state by cooling the sample rapidly down to room temperature. When the sample temperature was raised again to 70ﾟC, crystallization occurred in a company with crystal modification. These findings indicate chain foldings probably did not play an important role in the crystallization process in PB(dM)PP.More x-ray diffraction works by synchrotron experiments, in paticular, will be required to follow the whole process of crystallization of both the polymers. The works along this line will be continued in future.