Polyethylene oxide - iron thiocyanate polymeric complexes: thermal and mechanical properties

The thermal differential analysis of new polyethylene oxide (PEO)-Fe(SCN)3 solid blends reveals the presence of a single glass transition, which shifts to higher temperatures with increasing salt content. The observed features ensure the presence of strong polymer-salt interactions and the formation of homogeneous complexes on a scale of microscopic sizes. The temperature behavior of the dynamic elastic modulus, E?, and the internal friction in the region between 120 and 350 K is characterized by the presence of two relaxation mechanisms: the ?-process, at low temperatures, and the ?a- or primary relaxation, at high temperatures, which arise from local and cooperative segmental motions of the polymeric chains in the amorphous phase of the polymer respectively. The relaxation strength of both the processes increases by increasing salt concentration, a trend which parallels the decreasing degree of crystallinity of the polymer, as is also confirmed by the results of the thermal analysis. A quantitative interpretation of the ?-relaxation in terms of a Gaussian distribution of relaxation times permits one to obtain a useful insight in the microscopic origin of the relaxing centres.