Dielectric properties of poly[bis(trifluoroethoxy)phosphazene] and poly[bis(m-methylphenoxy)phosphazene]

Dielectric properties of poly[bis(trifluoroethoxy)phosphazene] (PFEP) and poly[bis(m‐methylphenoxy)phosphazene] (PmMPP) were studied in a temperature range from −195 to 120°C and at several frequencies between 0,1 and 100 kHz. In PFEP, two relaxations, an α relaxation above the glass transition temperature (Tg) and a β relaxation below Tg, which are related to a glass‐rubber transition and a local molecular motion of short segments, respectively, were observed. However, PmMPP shows no β relaxation. From the above dielectric results, it was concluded that side groups play an important role in molecular motion of the polyphosphazenes. In PmMPP a γ′ relaxation was found below Tg by immersing the polymers into water. The γ′ relaxation is related to the molecular motin of absorbed water.