Quasielastic light scattering in poly(methylmethacrylate)

Autor:	Alain Mermet, Nikolay V. Surovtsev, V. N. Novikov, Eugène Duval, T Achibat
Rok vydání:	1995
Předmět:	Quenching (fluorescence) Chemistry Relaxation (NMR) Activation energy Atmospheric temperature range Condensed Matter Physics Omega Molecular physics Light scattering symbols.namesake Nuclear magnetic resonance symbols General Materials Science Glass transition Raman spectroscopy
Zdroj:	Journal of Physics: Condensed Matter. 7:8077-8088
ISSN:	1361-648X 0953-8984
DOI:	10.1088/0953-8984/7/42/005
Popis:	Quasielastic light scattering (QLS) in the glassy polymer poly(methylmethacrylate) is investigated in the temperature range 12-470 K. Raman spectra were measured in the frequency interval 3-600 cm-1. The detailed temperature dependence of the Raman intensity at some fixed frequencies, omega =5, 8, 20 cm-1 is obtained. The influence of the quenching on the QLS is investigated. It is shown that there are two characteristic temperature regions with different dependences of the QLS intensity on temperature. The first one is for T 80-100 K. Here the relaxation time is nearly constant while the reduced Raman intensity increases with an activation energy of the order of 700 K up to the glass transition temperature Tg. The spectral dependence of the relaxation contribution, found by a subtraction of the lowest-temperature (12 K) spectrum from the current one, I(T, omega )/(n( omega )+1), demonstrates a relaxational beta peak which weakly depends on temperature. Its characteristic frequency is of the order of its width and is equal to 8-10 cm-1. The peak can be well fitted by a Lorentzian. The data obtained are considered within the frames of the existing models of QLS.
Databáze:	OpenAIRE
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