Low frequency near-IR Fourier transform Raman studies of hydrogen bonding in nylons

Low frequency Raman spectra of some nylon samples are presented. In order to ensure the reliability of near-IR (NIR) FT-Raman spectra at low frequencies, spectra obtained by excitation with a Nd—YAG laser are compared with spectra recorded with excitation in the visible region. Spurious laser emission lines appear due to the insufficiency of the spike filter at low frequencies. Samples of nylon 6, nylon 6.6 and nylon 12 are investigated. The NIR FT-Raman spectra are reliable down to approximately 50 cm−1, when corrections for spurious laser lines and spectrometer response are performed in a proper way. In order to avoid the influence of the intense Rayleigh line the spectra are also presented in the R( ν ) representation. A band around 100 cm−1 is assigned to a hydrogen bond mode. This band might depend upon the nylon structure.