DIPOLE-MOMENT AND DIELECTRIC-RELAXATION OF POLY(DIMETHYLSILAZANE) OLIGOMERS

The polarity of polysilazane chains is studied using as models hexamet hyldisilazane (HMDSZ) and an oligomer of amine-terminated poly(1,1-dim ethylsilazane) (PDMSZ). Solvent effects and the contribution of the at omic polarization to the dipole moment of both PDMSZ and HMDSZ are dis cussed. A qualitative interpretation of the dipole moment of the oligo mer suggests that gauche states about the skeletal bonds may be disfav ored with respect to the alternative trans states. The dielectric spec trum of PDMSZ presents a glass-rubber relaxation followed by two weak secondary absorptions. The experimental results show that the relaxati on strength DELTAepsilon of PDMSZ is lower than that corresponding to poly(1,1-dimethylsiloxane) (PDMS). The analysis of the glass-rubber re laxation by using the coupling scheme suggests that strong intermolecu lar interactions occur in the chains that presumably arise from hydrog en bonding interactions between amine groups. (C) 1993 John Wiley & So ns, Inc.