Effects of Molecular Structure on Segment Orientation in Poly(diethylsiloxane) Elastomers. 2. NMR Measurements from Uniaxially Stretched Samples

End-linked poly(diethylsiloxane) networks containing −CD2CH3 groups were studied in uniaxial extension by solid-state 2H NMR. Chain segment orientation was measured for samples at low extension ratios in the amorphous state. At higher extension ratios, a localized phase transition to a mesomorphic “neck” can occur. The mesophase content and segment orientation in the neck region were probed by NMR at various extension ratios. The effects of chemical cross-link density on segment orientation were deduced by studying a series of samples with varying molecular weight between cross-links.