Anomalous behavior of secondary dielectric relaxation in polypropylene glycols

A surprising slow down in the dielectric secondary gamma-relaxation with temperature increasing near the glass transition is confirmed for several polypropylene glycols. The peculiar behavior diminishes as the molecular weight grows. The minimal model (Dyre and Olsen 2003 Phys. Rev. Lett. 91 155703) is applied successfully to describe the temperature dependences of the gamma-relaxation times. The minimal model parameters are analyzed for different molecular weights. A molecular explanation of the gamma-process anomaly for polypropylene glycols is proposed on the basis of the minimal model prediction.