Ya.G. Urman

The shape of NMR line obtained in recording the second derivative of the absorption line in polymers

THE shape of nuclear magnetic resonance ( I~IR)l ines depends on the arrangement of the local magnetic field in the solid, and its s tudy provides information on molecular structure and mobility. Since van Vleck derived formulae [1] for the moment of NMR lines, most of the attention in experimental studies has been paid to the integral characteristics of the lines, since the second and fourth moments can be calculated theoretically and the shape of the line cannot be calculated in this case. But even a qualitative consideration of the shape of NMR lines may be very useful in studying polymers, for instance, where the line characteristic of slightly interacting CH~_ or CH 8_ groups, or two phase and two component systems is used [2]. Differential analysis, the s tudy of derivatives, is a particularly useful characteristic of line shape. In most ~YIR spectrometers the first derivative of the absorption line is usually recorded for broadened lines. Features of the shape, particularly where there is a point of inflexion, appear much more distinctly if the second derivative is recorded. This is quite frequently clone in E P R spectrometers [3], or in double resonance studies [4]. As far as we know, the method of recording the second derivative has not yet been used in NMR spectroscopy. The purpose of the present work was to find out the possibility of studying •MR in polymers by using the second derivative of the absorption line.