Dipole moment and dielectric relaxation of poly(dimethylsilazane) oligomers

The polarity of polysilazane chains is studied using as models hexamethyldisilazane (HMDSZ) and an oligomer of amine-terminated poly(1,1-dimethylsilazane) (PDMSZ). Solvent effects and the contribution of the atomic polarization to the dipole moment of both PDMSZ and HMDSZ are discussed. A qualitative interpretation of the dipole moment of the oligomer suggests that gauche states about the skeletal bonds may be disfavored with respect to the alternative trans states. The dielectric spectrum of PDMSZ presents a glass-rubber relaxation followed by two weak secondary absorptions. The experimental results show that the relaxation strength Δε of PDMSZ is lower than that corresponding to poly(1,1-dimethylsiloxane) (PDMS). The analysis of the glass-rubber relaxation by using the coupling scheme suggests that strong intermolecular interactions occur in the chains that presumably arise from hydrogen bonding interactions between amine groups. © 1993 John Wiley & Sons, Inc.