Abstract
We present a detailed study of the local dynamics of short polyethylene (PE) chains using molecular dynamics (MD) simulations and quasi-elastic neutron scattering (QENS) data. QENS measurements were carried out on two samples having different chain lengths: C44H90 and PE2K (Mw = 2150 g/mol). The incoherent dynamic structure factors obtained from experiments at T = 450 K and MD simulations carried out at the same temperature are compared in the range 0.5 ≤ Q ≤ 2.0 A-1. Agreement between experimental data and simulations is quantitative. Attempts are made to characterize the momentum transfer and the chain length dependence of the I(Q,t) and S(Q,ω) data on the basis of the Kohlrausch−Williams−Watts (KWW) function and two exponentials relaxation functions in time. As MD simulation data cover a broader frequency window and have a very low statistical noise, a more refined analysis of the intermediate scattering functions in terms of a continuous linear combination of exponentials weighted by a distribution o...
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