Dielectric Properties of Poly(vinyl Alcohol) Hydrogels Prepared by Freezing/thawing Technique

The dielectric behavior of poly(vinyl alcohol) –PVA– crosslinked hydrogels obtained by the repeated freezing/ thawing (F/T) technique have been investigated by dielectric relaxation spectroscopy (DRS) and differential scanning calorimetry (DSC). The crosslinked polymer is produced by the clustering of chains caused by the association of a polar group of the dissolved polymer followed by polymer crystallization. The dielectric spectra obtained from -50 °C to -10 °C show a broad secondary relaxation process associated to local mobility, ß relaxation, which is related to the terminal polar groups (OH). This process is strongly affected by the freezing/thawing cycles applied. The values of tan δ are below 1 indicating the dielectric phenomenon is predominant in all samples. The effect of crosslinking PVA on the dynamics of the secondary relaxation process was further analyzed.