Dynamics in complex systems: Dendrimer-polymer blends in electric and mechanical fields

An investigation was carried out on the molecular dynamics of blends composed of poly(amidoamine) (PAMAM) dendrimers with ethylenediamine core and amino surface groups (generations 0 and 3) and three linear polymers: poly(propylene oxide) - PPO and two block copolymers, poly(propylene oxide)/poly(ethylene oxide) - PPO/PEO with different mole ratios: 29/6 (amorphous) and 10/31 (crystalline). The results were generated over a broad range of frequency and temperature by Dielectric Relaxation Spectroscopy (DRS) and Dynamic Mechanical Spectroscopy (DMS). Dielectric spectra of dendrimers in the PPO matrix reveal a decrease in the time scale of normal and segmental relaxation with increasing dendrimer concentration. In the amorphous blends with 29PPO/6PEO matrix, no effect of concentration on the time scale of normal and segmental processes was observed. But in the crystalline blends with 10PPO/31PEO matrix, relaxation time increases with increasing dendrimer concentration. Results acquired by DRS and DMS were contrasted and the obtained relaxation times were found to be in excellent agreement. A detailed analysis of the effect of generation and concentration of dendrimers, hydrophilicity and morphology of the polymer matrix and temperature on the molecular origin, the shape of the relaxation spectra, the dielectric relaxation strength and the frequency location for the maximum loss in dendrimer-polymer blends is provided.