FTIR SEPARATION OF NYLON-6 CHAIN CONFORMATIONS - CLARIFICATION OF THE MESOMORPHOUS AND GAMMA-CRYSTALLINE PHASES

Specific infrared absorptions for each form of Nylon-6 have been identified. Quenched films were prepared by melt casting and converted in turn to the alpha-crystalline and gamma-crystalline structures. The films were examined using Fourier transform infrared spectroscopy (FTIR) with the attenuated total reflection configuration and by X-ray diffractometry. The FTIR spectrum of the pure mesomorphous component of the quenched film was calculated by subtracting away the contribution of alpha-crystalline peaks present due to incomplete quenching. A curve-fitting procedure was applied to the pure mesomorphous and gamma crystalline spectra. Several peaks in the mesomorphous spectrum are observed to develop a shoulder upon conversion to the gamma-crystalline form. This is due to the extra gauche character imparted to the C - N bond between the methylene unit and the amide group. These and other band assignments were confirmed by analysis of model compounds.