Deuterium n.m.r. is used to observe the change in segmental dynamics and orientation at the crystallization temperature T-c in a uniaxially stretched poly(dimethylsiloxane) (PDMS) network. Experiments are performed over a wide temperature range (235-294 K). The amorphous parts of the chains are probed via perdeuterated n-octane probe molecules dissolved in the network. H-2 n.m.r. spectra change drastically within a small temperature interval of 4 K in the vicinity of T-c. Above T-c, the spectra reflect the uniaxial dynamics of the octane probes. In the vicinity of T-c, the spectra are sensitive to the internal dynamics of the octane probe and indicate a heterogeneity in the mobility of the network chains. The isotropic lines obtained for T less than or equal to T-c confirm that the local constraints introduced by the external deformation disappear in the amorphous part of the sample in the presence of the crystalline phase.