SPHERULITIC MORPHOLOGY AND POLYMORPHISM O F POLY[BIS(3,4-DIMETHYLPHENOXY)PHOSPHAZENE]

Spherulitic morphology and phase transition of poly [bis(3,4-dimethylp henoxy)phosphazene] have been studied by optical microscopy, depolariz ed light-intensity measurements, DSC and X-ray diffraction. When the t hin film of the polymer in its mesomorphic state was cooled down at 5 degrees C/min to room temperature, several larger spherulites (B-type) appeared in the first stage, followed by development of a number of s maller spherulites (A-type). When the sample was heated subsequently, the A-type spherulites and B-type spherulites disappeared at 96 degree s C and 110 degrees C, respectively. These transition temperatures coi ncided with two DSC endothermic peaks. The extinction in the powder X- ray diffraction patterns of the spherulitic films indicated that therm odynamically less-stable alpha-type form (orthorhombic, primitive latt ice) melted out in the vicinity of 100 degrees C, but the beta-type fo rm (orthorhombic, base-centered lattice) remained. The A-type spheruli tes and B-type spherulites were composed of alpha-type crystals and be ta-type crystals, respectively.