Dynamic mechanical relaxations in poly(oxyoctamethylene)

Dynamic mechanical, calorimetric and X‐ray diffraction measurements of poly(oxyoctamethylene) are carried out, in order to determine its viscoelastic relaxations and to elucidate the influence of the crystalline form of this polyether on its degree of crystallinity. The dynamic mechanical measurements were performed using a dynamic viscoelastometer at four frequencies ranging from 3,5 to 110 Hz, in the temperature range from −150°C to 60°C. Two relaxations are observed. The one occurring at the lowest temperature (−139°C at 3,5 Hz) has an activation energy of 10 ± 1 kcal/mol (42 ± 4 kJ/mol) and is considered as the γ relaxation which takes place in all the polymers with three or more adjacent methylenic units. The other one appears at −24°C and its activation energy is higher than 100 kcal/mol. The assignment of other of the two relaxations as glass transition of the polymer is discussed in context of the relaxation maxima of other members of the polyether series.