The segmental orientation of uniaxially strained poly(l,4-butadiene) networks was probed by deuterium magnetic resonance over a wide range of extension ratios. The experiments were performed on homogeneously deuterated networks and on partially deuterated networks with short deuterated segments at network junctions. The analysis of the strain-dependent line shapes of the deuterium resonances is interpreted in terms of a nonaffine deformation mechanism by means of which short elastically effective chains are stretched to a greater extent than long chains. Comparison of homogeneously and junction deuterated networks gives evidence of inhomogeneous deformation of individual chains with an excess orientation near network junctions.

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and IBM, France, for making the visit of C. E.W. to SSRL possible. We also acknowledge B. Schechtman (IBM, San Jose), A. Bienenstock (SSRL), and Ph. Teyssié (Liege) for their efforts and encouragement during this work. We further thank the staff at SSRL for their assistance throughout the course of this work. R.J. and J.H. are also indebted to the Service de la Programmation de la Politique Scientifique (Brussels) for financial support.

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