Fermi resonance in the infrared spectra of Nylon-11

Nylon-11 is prepared by casting from the solvents trifluoroacetic acid and m-cresol and by melt-crystallization. Room-temperature infrared spectra are compared in terms of possible crystal structures. The spectra are examined for the presence of Fermi resonance which occurs between the N-H stretching fundamental mode and the overtone and combination modes of the amide I and II vibrations. An analysis of peak frequencies and intensities is used to provide support for the assignment of the amide II overtone and the amide I + II combination modes. A newly observed peak in the spectra is assigned to the amide I overtone. Symmetry considerations are discussed which predict the resonance of the overtone and combination modes with the N-H stretching fundamental. © 1992 John Wiley & Sons, Inc.