Reorientational Dynamics of Polyethylene Glycol/PAMAM Dendrimer Blends

The reorientational dynamics of dipoles in a series of blends of Polyethylene Glycol (PEG) and poly(amidoamine) (PAMAM) dendrimers were investigated by broadband dielectric relaxation spectroscopy (DRS). Measurements were performed over a wide range of frequency and temperature. Neat PEG exhibits three relaxation processes: the segmental process in the amorphous phase and two faster processes due to the localized motions in the amorphous regions and the rotation of hydroxyl end groups. Addition of dendrimers to the PEG matrix slows down the segmental process in the amorphous phase, but has no effect on the relaxation time of local processes in PEG. However, H-bonding which forms between the PEG oxygen and the amino groups on dendrimer surface is responsible for a shift of local processes in dendrimers to lower frequency. A detail analysis of the effect of temperature, concentration of dendrimers and molecular weight of PEG on the relaxation dynamics is offered.