Water dependence of the dielectric β-relaxation in poly(ε-caprolactone)

Water dependent secondary relaxations are well known in glass formers. In Poly(ε-caprolactone) (PCL) both the dielectric and mechanical β-relaxation have a water dependent relaxation strength, whose molecular reasons are still unclear. By systematically varying the water content of the samples, a linear dependency between the dielectric relaxation strength and the number of absorbed water molecules was found, leading to a vanishing relaxation for completely dried samples. Neither the α-relaxation nor the secondary β-relaxation showed water dependent relaxation times and also the glass transition temperature determined by differential scanning microscopy (DSC) is not affected by the water absorption. So far the molecular origins of the dielectric β-relaxation in PCL are not consistent with the observations in other glass formers.