NMR spectroscopy polymers

Bovey, F. A. Polymer NMR Spectroscopy. VI. Methyl methacrylate-styrene... 

Bovey, F. A., and G. V. D. Tiers Polymer NMR spectroscopy. II. The high resolution spectra of methyl-methacrylate polymers prepared with free radical and anionic initiators. J. Polymer Sci. 44, 173—182 (I960). 

NMR spectroscopy is capable of distinguishing between the different types of NMR unsaturation that can occur in a polymer. NMR spectroscopy has been used to determine unsaturation in acrylonitrile-butadiene-styrene terpolymers (ABS) [33, 34], 1,2-polybutadiene [34, 35], ethylene-propylene terpolymers [35], and vinyl chloride-vinylidene chloride copolymers [10, 36, 37]. 

The reader is assumed to be familiar with basic ID- and 2D-NMR techniques for organic and polymeric structure studies, which might be achieved by reading a text such as that by Silverstein et al. [1] and a recent review on polymer NMR spectroscopy [2]. 

The first report of 2D-NMR experiments by Ernst et al. lead to explosive growth in the use of NMR to study complex molecules such as synthetic polymers. The most significant advances in polymer NMR spectroscopy over the past two decades have been the constmction of instruments with stable electronics, and the development of powerful computers and software for the collection, processing, and examination of 2D-NMR spectra. 

The use of NMR spectroscopy to characterize copolymer microstructure takes advantage of this last ability to discern environmental effects which extend over the length of several repeat units. This capability is extremely valuable in analyzing the stereoregularity of a polymer, and we shall have more to say about it in that context in Sec. 7.11. 

It is not the purpose of this book to discuss in detail the contributions of NMR spectroscopy to the determination of molecular structure. This is a specialized field in itself and a great deal has been written on the subject. In this section we shall consider only the application of NMR to the elucidation of stereoregularity in polymers. Numerous other applications of this powerful technique have also been made in polymer chemistry, including the study of positional and geometrical isomerism (Sec. 1.6), copolymers (Sec. 7.7), and helix-coil transitions (Sec. 1.11). We shall also make no attempt to compare the NMR spectra of various different polymers instead, we shall examine only the NMR spectra of different poly (methyl methacrylate) preparations to illustrate the capabilities of the method, using the first system that was investigated by this technique as the example. 

R. Komoroski, ed.. High Resolution NMR Spectroscopy of Synthetic Polymers in Bulk, VCH Pubhshers, New York, 1986. 

Chain Structure. The chemical composition of poly (vinyhdene chloride) has been confirmed by various techniques, including elemental analysis, x-ray diffraction analysis, degradation studies, and in, Raman, and nmr spectroscopy. The polymer chain is made up of vinyhdene chloride units added head-to-tail ... 

The classic chemical technique for measuring the degree of unsaturation in diene polymers is iodometry (iodine value) [102]. Kubo et al. [103] extensively measured the iodine value to determine the amount of residual double bonds present in the HNBR. However, this method exhibited significantly poorer precision as compared with IR and NMR spectroscopies [99-101]. Acid... 

The resulting ladder polymer LPPP 12 possesses a number average molecular weight of 25000, which corresponds to the incorporation of 65 phenylene units. No structure defects could be detected using NMR spectroscopy. LPPP 12 is... 

Hatada, K. NMR Spectroscopy of Polymers-, Springer-Verlag Berlin, 2003. 

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. 

Tonelli, A.E. NMR Spectroscopy and Polymer Microstructure VC1I New York, 1989. 

Axelson DE (1986) in Komoroski (ed) High-resolution NMR spectroscopy of synthetic polymers in bulk. VCH, Weinheim, Chaps. 5 and 6... 

Tonelli AE (1989) NMR spectroscopy and polymer microstructure the conformational connection. VCH, Weinheim... 

Another definition, taking into account polymerization conversion, has been more recently proposed.192 Perfect dendrimers present only terminal- and dendritic-type units and therefore have DB = 1, while linear polymers have DB = 0. Linear units do not contribute to branching and can be considered as structural defects present in hyperbranched polymers but not in dendrimers. For most hyperbranched polymers, nuclear magnetic resonance (NMR) spectroscopy determinations lead to DB values close to 0.5, that is, close to the theoretical value for randomly branched polymers. Slow monomer addition193 194 or polycondensations with nonequal reactivity of functional groups195 have been reported to yield polymers with higher DBs (0.6-0.66 range). 

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