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Well-defined poly(dimethylsiloxane) networks containing a known fraction of labeled elastic chains were obtained by cross-linking mixtures of deuterated and undeuterated functional precursor polymers. Small-angle neutron scattering experiments on polymer melts, on semidilute solutions, and on dry and swollen networks show that the single intrachain form factor can be extracted from the scattered intensities even when the volume fraction of labeled polymer is high. The chain dimensions are not changed by the cross-linking process. The radius of gyration of an elastic chain in the unswollen network and that of the corresponding "free" chain in the melt are identical. The Gaussian character of the network chains has been confirmed with a high precision.

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2014 L'ordre orientationnel induit dans un réseau élastique sous contrainte uniaxiale est étudié par RMN du deutérium. Les spectres de chaînes perdeutérées d'un réseau modèle de polydiméthylsiloxane sous tension ou compression présentent un doublet quadrupolaire. Des expériences pour différentes orientations de la contrainte par rapport au champ magnétique du spectromètre montrent qu'une anisotropie uniaxiale est mesurée au niveau des segments du polymère. De plus l'écartement du doublet a une dépendance explicite en fonction du taux d'élongation. Abstract. 2014 The orientational order generated in a cross-linked rubber by a uniaxial stress is probed with deuterium NMR. Spectra of perdeuterated polymer chains of a polydimethylsiloxane model network exhibit quadrupolar doublets under both elongation and compression. Experiments for various orientations of the stress relative to the spectrometer magnetic field show that an uniaxial anisotropy is induced at the level of the chain segments. The doublet splitting has an explicit dependence on the extension ratio.