NMR OBSERVATION OF POLY(ETHYLENE OXIDE) DYNAMICS IN A POLY(METHYL METHACRYLATE) MATRIX - EFFECT OF CHAIN-LENGTH VARIATION

The molecular weight dependence of the proton transverse nuclear magnetic relaxation rate of poly(ethylene oxide) (PEO) blended with deuterated poly(methyl methacrylate) (PMMA) of molecular weight 5.1 X 10(4) is reported. Two domains of chain dynamics are observed in the molten state. For PEO molecular weights M(w) less than 2.5 X 10(4), the chain length dependence of the relaxation rate 1/T2 scales as M(w)beta with beta almost-equal-to 0.9. For higher molecular weights (2.5 X 10(4) < M(w) < 6.5 X 10(4)) the data are analyzed by assuming a partition of each chain into submolecules. These submolecules have a molecular weight which is close to that of the submolecule, M(e) almost-equal-to 7 X 10(3), derived from the plateau modulus measurement of this mixture at the same concentration and already reported in the literature.