A series of end-linked PDMS networks synthesized with different molar mass precursor chains is examined using H-2 NMR spectroscopy. The resulting line Shapes for networks in the undeformed state show clear differences with precursor chain molar mass. Furthermore, samples uniaxially extended to high extension ratio show a clear shoulder in the line shape and two characteristic splittings (two doublets). Comparison with spectra for deuterated free chains dissolved in an unlabeled network confirms that the inner doublet results from excluded volume interactions between segments whereas the outer doublet is clue to more highly aligned chain segments from chains with conformations trapped by the cross-linking reaction.