Effects of entanglements on the single-chain motion of polymer molecules in melt samples observed by neutron scattering

Abstract

The motion of single molecules of polytetrahydrofuran in melt samples of deuterated polytetrahydrofuran has been observed using high-resolution quasi-elastic neutron scattering (the neutron spin-echo technique). Comparison of results for two systems in which the matrix of deuterated molecules surrounding the observed molecules is either well above or well below the entanglement molecular weight shows clearly the effects of molecular entanglements on the observed correlation functions. The form of these correlation functions agrees with the theoretically predicted behaviour for entangled systems and allows a value for the average distance between entanglements of 30 Å to be extracted.