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College Park, Maryland      June 6 - 10 , 2004

WP49: Low Energy Excitation of Poly(methyl methacrylate)

M.-H. Kim, C.M. Brown (NIST Center for Neutron Research; Department of Materials Science and Engineering, University of Maryland)

The relative contributions of poly(methyl methacrylate) side groups (ester, alpha-methyl, and main chain CH2) to the low energy Boson excitation were studied by isotopic substitution using the Fermi-Chopper Time-Of-Flight Neutron Spectrometer. The enhancement of the dynamic structure factor, S(Q, ω) observed around 1.8 meV is dominated by the methyl vibration on the ester group(-COOCH3). The relative contributions follow the order -COOCH3>> -alpha-CH3> -CH2-.

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