Dielectric Relaxations in a Hyperbranched Polyester with Terminal Hydroxyl Groups: Effects of Generation Number

Abstract

Relaxation processes in a hyperbranched polyester with terminal hydroxyl groups have been investigated. The study emphasizes the molecular weight dependence of conductivity and γ-relaxations as the α- and β-relaxations are masked by the conductivity. It is found that the conductivity relaxation follows a non-Arrhenius dependence while the γ-relaxation follows an Arrhenius dependence. There is a slight increase in the temperature location of the γ-relaxation with generation. The activation energies of the conductivity relaxation and γ-relaxation decrease with increasing generation number from the second to the fourth. This behavior is rationalized by relating molecular weight dependence of the chain end concentrations and possible conformational changes of the hyperbranched macromolecules.