Bovey

The first studies of polymers by nmr were published only about a year after the first reports of the observation of the NMR phenomenon in bulk matter by Bloch and Purcell in 19 6. This early work concerned the solid state, which for the following decade was the sole object of nmr investigations of polymers. By measurements of nuclear relaxation, involving for the most part protons, much important information concerning chain dynamics of a variety of polymers has been gathered. 

In the earlier era of high resolution nmr, when the study of small molecules had reached a fairly advanced state, it was still generally assumed that very large molecules could not give useful spectra even in solution because of their supposedly slow motions, as evidenced by the very high viscosities of such solutions. There was also a feeling that the spectra would be too complex to interpret. 

Among the most useful findings was the observation that proton nmr could be employed, —even with the low frequency spectrometers of the time—, to obtain quantitative information concerning the stereochemistry of vinyl polymers. The Ziegler-Natta revolution was then relatively new and was still generating much excitement. 

In the classical researches of Natta and his collaborators. X-ray fiber diagrams were the principal structural tool . This method required that the polymer be crystallized, which was often difficult or impossible. Despite its great power. X-ray was subject to errors of interpretation and often failed to reveal significant structural details. 

The a-methyl resonances centered at ca. 9t(16) could also be interpreted to give quantitative estimates of isotactic (abbreviated mm) and syndiotactic (rr) triad sequences of monomer units, and also of the mixed unit mr, termed heterotactic, which must occur in chains which are not perfectly stereoregiilar  

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Figure 7.11 Methylene proton portion of the 220-MHz NMR spectrum of poly(methyl methacrylate) (a) predominately syndiotactic and (b) predominately isotactic. [From F. A. Bovey, High Resolution NMR of Macro molecules, Academic, New York, 1972, used with permission.]...

Bovey, F. A., High Resolution NMR of Macromolecules, Academic, New York, 1972. 

F. Bovey and co-workers. Emulsion Polymerisation, Vol. 10, High Polymers, Interscience PubHshers, New York, 1955. 

BOVEY, F. A. and winslow, f. h. (Eds.), Macromolecules—An introduction to polymer science. Academic Press, New York (1979)... 

In contrast to this expansion in the primary sources of data, secondary F-NMR literamre coverage has declmed Fields [7d], Jameson [77], and Bovey[7S] have contnbuted noteworthy fluorine NMR chapters m recendy published books Jameson s review [17] presents tables and figures viv idly displaying the magnitude... 

Bovey, F A, Jelmski, L, Mirau, P A Nuclear Magnetic Resonance Spectroscopy, 2nd ed, Acadermc Press New York, 1988 Proton and Fluorine Nuclear Magnetic Resonance Spectral Data, Vanan Instruments/Japan Halon Tokyo, 1988... 

Detailed discussion of polymer tacticity can be found in texts by Randall,2 Bovey,1-3 Koenig,4-5 Tonelli6 and Hatada.7 In order to understand stereoisomerism in polymer chains formed from mono- or 1,1-disubstiluted monomers, consider four idealized chain structures ... 

The application of NMR spectroscopy to tacticity determination of synthetic polymers was pioneered by Bovey and Tiers.9 NMR spectroscopy is the most used method and often the only technique available for directly assessing tacticity of polymer chains. "2 7 8 0JI The chemical shift of a given nucleus in or attached to the chain may be sensitive to the configuration of centers three or more monomer units removed. Other forms of spectroscopy (e.g. TR spectroscopy l2 lJ) are useful with some polymers and various physical properties (e.g. the Kerr effect14) may also be correlated with tacticity. 

Bovey, F.A, Polymer Conformation and Configuration, Academic Press New York, 1969. 

The kinetics and mechanism of retardation and inhibition has been reviewed by Bamford,173 Tiidos and Foldes-Bere/snieh,174 Eastmond,1 5 Goldfinger el /. 6 and Bovey and Kolthoff.1 n... 

NMR spectroscopy has made possible the characterization of copolymers in terms of their monomer sequence distribution. The area has been reviewed by Randall,100 Bovey,139 Tonelli,101 Hatada140 and others. Information on monomer sequence distribution is substantially more powerful than simple composition data with respect to model discrimination,25,49 Although many authors have used the distribution of triad fractions to confirm the adequacy or otherwise of various models, only a few25 58,141 have used dyad or triad fractions to calculate reactivity ratios directly. 

Bovey, F.A. Chain Structure and Conformation of Macromolecules Wiley New York, 1982. 

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