Anomalous behavior in blends of a polychlorinated biphenyl with polystyrene oligomer investigated by mechanical and dielectric spectroscopy

Dynamic mechanical and dielectric spectroscopy measurements on a polychlorinated biphenyl (PCB54), an oligomeric polystyrene (PS590), and their blend revealed various anomalies: (i) The mechanical relaxation times were always smaller (faster relaxation) than the relaxation times extracted from the dielectric modulus. (ii) The fragility (T-g-normalized temperature dependence of the relaxation times) for the two. neat materials was the same, even though the shapes of the corresponding relaxation functions were quite different. Such a result is at odds with the well-established correlation between these. quantities. (id) The addition of PS590 speeds up dielectric relaxation of the PCB54, even though the former has a higher glass transition temperature. However, the mechanical response is normal; that is, the relaxation times of the mixture are intermediate between those of the pure components. A brief discussion of these anomalies is given.