Debye-Waller factors in amorphous polymers

The Debye-Waller factors of amorphous polystyrene and amorphous polybutadiene have been determined from neutron time-of-flight data using two different methods. The first uses the Q-dependence (Q momentum transfer) of the elastic intensity in the conventional way. The second employs the Q-dependence of the inelastic scattering. The mean square displacement measured at low frequencies in the inelastic region turns out to be significantly larger than the elastic value. The effect is more pronounced for polystyrene than for polybutadiene.