Multinuclear Solid State NMR Study of Phase Transition in Poly[bis (4-ethylphenoxy)phosphazene].

The phase transitions of poly[bis(4-ethylphenoxy)phosphazene] have been studied by solid state sup 31 P and sup 13 C NMR for the first time. There are a number of transitions observed around 100C, which strongly depend on the thermal history. The highest temperature transition T(1) is assigned to the solid to liquid crystal transition from the abrupt change of motional state of the polymer and also from x-ray diffraction and optical microscope observation. The sup 31 P spectra show three backbone conformations corresponding to crystalline, interfacial, and amorphous phases below T(1). The sup 31 P chemical shift of the backbone in the amorphous phase is about the same as that in the liquid crystalline phase, indicating the dynamical disorder of backbone conformations in both phases.