Secondary relaxation in two engineering thermoplastics by neutron scattering and dielectric spectroscopy

We present a preliminary investigation of the dynamics of glassy polycarbonate (PC) and polysulfone (PSF) by means of quasielastic neutron scattering and dielectric spectroscopy. Whereas the consideration of pure phenylene ring π-flips is enough to explain the momentum-transfer (Q) dependence of the inelastic intensity measured for PSF, in the case of PC the Q dependence of both the coherent and the incoherent scattering functions reveal the existence in this polymer of some more complex motion of the phenylene ring. On the other hand, the similarity of the energy landscapes deduced from the different techniques points to a closely related molecular origin for all the relaxation/motions observed.We acknowledge the Basque Government, ‘Donostia International Physics Center’, Iberdrola S.A., and the support of the following research projects: DGICYT, No. PB97-0638; GV, No. EX 1999-11; and UPV/EHU, No. 206.215-G20/98.Peer reviewe