Nuclear Magnetic Resonance of Polymers in Solution

IR has been used in addition to many other techniques to anaiyze poiymer and copoiymer compositions, either by itseif or in addition to other techniques. Recentiy, the characterization by spatiai differentiation of submicrometer domains in poly(hydroxyalkanoate) copolymer by the combination of atomic force microscopy (AFM) and IR spectroscopy was reported [9, 10]. This new capability resulting from the combination of two single instruments enables the spectroscopic characterization of microdomainforming polymers at levels not previously possible. 

NMR is now a powerful analytical technique that has widespread applications in all areas of chemistry, including polymer characterization. Using NMR for elucidating the molecular structure of an unknown sample of polymer, accurate information can be obtained for qualitative and quantitative analyses of polymeric materials. 

NMR is basically another form of absorption spectrometry that can be used in addition to IR, or UV, spectrometries. It is based on the absorption of electromagnetic radiation under appropriate conditions in the radio-frequency region at frequencies defined by the nature of the sample. Absorption is a function of each nucleus in the molecule. The main purpose of this technique is to provide information for the identification of organic molecules by studying the magnetic properties of nuclei. 

All nuclei carry a charge. In some nuclei, this charge spins on the nuclear axis, and this circulation of nuclear charge generates a magnetic dipole along the axis (Fig. 16.7). 

The angular momentum of the spinning charge can be described in terms of spin numbers, having the values of 0, 1/2, 1, 3/2, etc., where 0 denotes no spin like in i 0,32s, etc. For these elements, NMR experiments cannot be conducted since there is no spin angular moment and thus no magnetic moment to be analyzed. Several nuclei, however, such as H, h, i9p sip 

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