CC BY 4.0 UnportedWiesner, BrigitteKohn, BenjaminMende, MandyScheler, Ulrich2023-01-262023-01-262018https://oa.tib.eu/renate/handle/123456789/11074http://dx.doi.org/10.34657/10100The local dynamics in polymer melts and the impact of external shear in a Couette geometry have been investigated using rheological nuclear magnetic resonance (NMR). The spin-spin relaxation time, T2, which is sensitive to chain-segment motion, has been measured as a function of shear rate for two samples of poly(dimethylsiloxane). For the low-molecular-weight sample, a mono-exponential decay is observed, which becomes slightly faster with shear, indicating restrictions of the polymer chain motion. For the high-weight sample, a much faster bi-exponential decay is observed, indicative of entanglements. Both components in this decay become longer with shear. This implies that the free polymer segments between entanglements become effectively longer as a result of shear.enghttps://creativecommons.org/licenses/by/4.0/540EntanglementsPolymer mobilityRheo NMRArticle