College Park, Maryland      June 6 - 10 , 2004

T3-B1 (3:45 PM): The Influence of Environment on Polymer Mobility: Quasielastic Neutron Scattering on PEO/PMMA Blends (Invited)

J. K. Maranas, V. Garcia-Sakai, C. Chen (Pennsylvania State University), Z. Chowdhuri, I. Peral, N. Rosov (National Institute of Standards and Technology)

The focus of this presentation is the use of quasielastic neutron scattering to assess mobility in polymers. Background on the dynamic behavior of polymers on time-scales assessable by neutron instruments will be covered. We are interested in the changes in this mobility when the environment of the polymer is changed in some way. One might imagine doing so by introducing nanoparticles, placing a neat polymer in a mixture, or incorporating the polymer as a di- or tri-block copolymer materials with nanoscale ordered regions. One of these manipulations, changes that occur when the polymer is placed in a mixture, will be illustrated with measurements made over the last year on backscattering, time-of-flight and neutron spin echo spectrometers on a blend of poly(methyl- methacrylate) [PMMA] and poly(ethylene oxide) [PEO]. These two constituent polymers have dynamic behavior separated by many orders of magnitude, a behavior that we find persists in the mixture using incoherent scattering with selective deuteration to isolate the dynamic responses of each component in turn. One challenge faced with this system is the extremely stretched nature of the relaxations the decay is very slow and thus not much is observed within the typical time windows of neutron spectrometers. Another challenge is to separate each components motion in coherent measurements where labeling is less helpful. We will discuss the potential for using chemically realistic simulations to assist in meeting these challenges.

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