Section 6. Chemical and physical properties Neutron scattering and the glass transition in polymers ± present status and future opportunities D. Richter a, * , M. Monkenbusch a , A. Arbe b , J. Colmenero b,c a Institut f ur Festk orperforschung, Forschungszentrum J ulich, D-52425 J ulich, Germany b Departamento de Fisica de Materiales, Universidad del Pais Vasco and Unidad de Fisica de Materiales CSIC-UPV/EHU), Apartado 1072, E-20080 San Sebastian, Spain c Donostia International Physics Center, Apartado 1072, E-20080 San Sebastian, Spain Abstract We present results obtained by the exploration of molecular motions by neutron scattering and outline future op- portunities resulting from methodological progress in high-resolution neutron spectroscopy. Starting on methododical grounds, we will commence with possible future developments in neutron spin echo spectroscopy NSE), the prime technique for the observation of molecular processes in the nanosecond domain. After describing the scope of neutron scattering for experiments on glass-forming materials, we will present measurements of the self-correlation function, which include the b-relaxation in polyisobutylene, and address the problem of the heterogeneity of the a-process. Thereafter,wedealwithdierentaspectsofthepaircorrelationfunction,startingfromcoherentscatteringexperiments onpolybutadiene,wherethechoiceofthemomentumtransferisselectivefortheobservationofthe a-or b-relaxation. Then, we emphasize results on the structural relaxation obtained for the dierent polymers at the ®rst structure factor peak.Finally,byexample,wewilladdressthecapabilityofneutronscattering,todealwithmotionsinpolymerblends, wherebyjudiciouslabelingthedynamicsofthedierentcomponentscanbeobservedseparately. Ó 2001Publishedby Elsevier Science B.V. PACS: 61.41.+e; 61.12.Ex; 61.25.H 1. Introduction Neutron scattering provides space and time resolution on atomistic length and time scales si- multaneously. This unique property goes along with a limited dynamic range and restrictions in long time observation which are important in studies of the glass transition. It has been shown that a combination of spectroscopic techniques such as dielectric spectroscopy with neutron spin echo spectroscopy NSE) can be advantageous to bridgethisde®ciency[1±6].Inthisshortreview,we will put some emphasis on an additional facility oered by neutron scattering which is opened by the dierent scattering properties of hydrogen and deuterium. Synthetic chemistry allows judicious hydrogen deuterium labeling of polymers and fa- cilitates the observation of speci®c dynamic prop- erties in polymeric systems. Due to the magnitude of the incoherent cross-section of hydrogen, in protonated materials the self-correlation function Journal of Non-Crystalline Solids 287 2001) 286±296 www.elsevier.com/locate/jnoncrysol * Corresponding author. Tel.: +49-2461 61 2499/5774; fax: +49-2461 61 2610. E-mail addresses: d.richter@fz-juelich.de D. Richter), m.monkenbusch@fz-juelich.de M. Monkenbusch), wapar- mea@sc.ehu.es A. Arbe), wapcolej@sc.ehu.es J. Colmenero). 0022-3093/01/$ - see front matter Ó 2001 Published by Elsevier Science B.V. PII:S0022-309301)00631-7