ABSTRACT
Nuclear magnetic resonance (NMR) spectroscopy is one of the most versatile techniques available to the analyst of plastics and other polymeric materials. Atomic nuclei respond to external magnetic fields and radiofrequency excitation in complex, but wellunderstood, ways, and the spectroscopist can exploit these interactions in many different ways. Dipolar and quadrupolar couplings extend along chemical bonds or through space, chemical shifts are extremely sensitive to the identities and positions of neighboring atoms, and scalar couplings reveal details of chemical structure. Each of these features could make a viable analytical tool on its own, but the real power of NMR arises from its ability to express, suppress, or correlate these interactions through experimental manipulations. One-, two-, and higher-dimensional spectroscopies provide the most detailed descriptions of polymer microstructure available from any characterization method, whether the sample is a solution or a solid. Measurements of nuclear relaxation, chemical shielding, and spin-spin interactions reveal details of the morphology and dynamics of polymer systems. Advances in medical imaging are beginning to be applied to materials, and NMR is becoming an important technique for monitoring resin properties on-line.
