| Abstract: | A linear dimethylpolysilazane polymer has been prepared and its internal motion studied by the techniques of broadline nuclear magnetic resonance. Second moments and line widths are reported as a function of temperature from ?196 to 30°C. The results are compared to those for linear dimethylpolysiloxane, as well as to those for the crosslinked siloxane and silazane. The experimental low-temperature second moment of 7.25 ± 0.5 gauss2 corresponds to a C3 reorientation of methyl groups about the silicon–carbon bond. The motions occurring in the silazane are found to be the same as those in the corresponding siloxane. The transition to low second moments occurs approximately 30°C. higher in the linear silazane than in the linear siloxane. This is attributed to a somewhat greater resistance to motion in the silazane. |
