TSC and Broadband Dielectric Spectroscopy Studies of β Relaxation in Phosphorus-Containing Dendrimers

With their self-similar architectures, dendrimers constitute good models of complex structures. After Vo¨gtle’s results,1 further investigations have intended to increase the generation number.1,2 The state of the art is reached with phosphorus-containing dendrimers3 (12th generation). The aim of this work is to analyze the evolution of molecular mobility upon increasing of generation. Thanks to complementary dielectric techniques as thermostimulated currents (TSC) and dynamic dielectric spectroscopy (DDS), the mechanism of dipolar polarization and its evolution as a function of the generation of dendrimers will be studied. DDS shows the shift of relaxation mode on a wide frequency and temperature range as being shown previously.5-8 Owing to its low equivalent frequency and its high sensibility, TSC experiments give complementary information on the elementary components of the complex relaxation. Moreover by using fractional polarization, the experimental distribution function of the activation parameters has been determined. In this communication, we focus on low-temperature relaxations of phosphorus-containing dendrimers of generations 0, 1, and 2