Frequency dependence of nuclear magnetic resonance parameters in poly(methyl methacrylate)

ABSTRACT:The frequency dependences of 13 C spin-lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE) of poly(methyl methacrylate) (PMMA) in CDCI3 solution have been analyzed in terms of different models describing the motions of the C-H internuclear vector. Box-type and log-x 2 distribution models of correlation times as well as the 2T model assuming two independent motions are inadequate to explain simultaneously the frequency dependences of T1 and NOE values for backbone CH2 , IX-CH 3 , and OCH3 carbons. In contrast, those frequency dependences can be well interpreted by the 3T model in which three superimposed motions with correlation times of the orders of 10-12 , 10-10 , and 10-9 s are assumed. This indicates that the backbone motion of PMMA should be described in terms of at least three types of superimposed motion and thus one or two additional motions may be overlapped for the side-group carbons.KEY WORDS 13 C NMR I Poly(methyl methacrylate) I Round Robin Method I Spin-Lattice Relaxation Time I Nuclear Overhauser Enhancement I Frequency Dependence I Molecular Motion IThe local motions of polymers in solution have been investigated by a number of spectroscopic techniques. Among these techniques 13 C NMR spectroscopy is very powerful in analyzing the detailed motions for the respective carbon nuclei which constitute polymeric -------· · --------t The following names should be succeeded as the.

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Frequency dependence of nuclear magnetic resonance parameters in poly(methyl methacrylate)

Cited by 2 publications

References 11 publications

Applications of Labelling and Multidimensional NMR in the Characterization of Synthetic Polymers

Applications of Labelling and Multidimensional NMR in the Characterization of Synthetic Polymers

NMR Measurements of Identical Polymer Samples by Round Robin Method III. Analysis of Frequency Dependences of 13C Spin-Lattice Relaxation Times and Nuclear Overhauser Enhancements

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