Poly(organophosphazenes) with Azoxybenzene Side Groups. Synthesis and Morphology

Azoxybenzene derivatives with chiral alkoxy terminal units were introduced as side chains in poly(organophosphazenes). The thermal behavior, morphology, and related electrical properties were investigated by using differential scanning calorimetry (DSC), X-ray diffraction, and measurements of the pyroelectric coefficient. From the DSC studies, suppression of side-chain crystallization by the azoxy group was evident. The thermal behavior was dependent on the spacer length and on the structure of the terminal units on the azoxybenzene group. A polyphosphazene with triethyleneoxy spacer units and azoxybenzene groups, with a 2-octoxy terminal unit at the para position, was amorphous and showed only a glass transition. However, 2-butoxy and 2-methyl-l-butoxy terminal groups imposed a layered morphology on the polymers. An X-ray diffraction study suggested that these polymers have a tilted layer morphology. Spontaneous polarization for the aligned polyphosphazenes was measured by integration of the pyroelectric coefficient with respect to temperature.