Signature of reptation in the long-time behavior of the deuteron NMR Free Induction Decay in high molecular mass polymer melts

Abstract

The classical tube-reptation (TR) model is based on the assumption, that in entangled polymer melts diffusion takes place inside the effective tubes having a conformation of ideal chains and being stable on the time scale of the terminal relaxation time τt, the latter being strongly molar mass (M) dependent. We argue, that this assumption leads for high M to a characteristic, strongly non-exponential time dependence of the deuteron Free Induction Decay, or likewise of the Hahn Echo amplitude. This holds for times t satisfying the condition τe≪T2<t≪τt, where T2is an effective spin-spin relaxation time andτe is the entanglement time.