Dynamic form function of a long polymer constrained by entanglements in a polymer melt

(Received 2 December 1992, revised 3 February 1993, accepted 26 March 1993)

Abstract
The dynamic form function of a long polymer in a polymer melt is calculated by assuming that, in the intermediate time region, the entanglement points remain fixed. The calculation agrees with the reptation concept of de Gennes. The results recall those of Ronca but are more exact, as we show by comparing them with the experimental spin echo neutron scattering data by D. Richter et al. The form function, is expressed in terms of pure numbers depending only on two parameters, namely the mean square distance between entanglements and a coefficient characterizing the continuous Rouse equation of the polymer.