Infrared Spectra of Polymers. I. Effect of Crystallinity on the Infrared Spectrum of Polyethylene and on the Infrared Spectra of Nylon 6 and Nylon 11

The melt and polarization spectra of dotriacontane and polyethylene in the 750–1500 cm—1 region and of nylon 6 and nylon 11 in the 450–4000 cm—1 region are presented. In addition, the melt and crystal spectra of stearone are presented in the 650–3500 cm—1 region. The effect of crystallinity on the spectrum of polyethylene is discussed. With the aid of published Raman spectra of crystalline hydrocarbons, an assignment of frequencies for polyethylene is made. The effect of crystallization on the spectrum of stearone is discussed and unusual features pointed out. Orientations in films of nylon 6 and nylon 11 are shown to be in the extrusion direction. The effect of melting on the hydrogen bonding and on the CO and NH frequencies is discussed. A partial assignment and classification of frequencies is made. When the films are melted, certain peaks vanish. These are ascribed to splitting arising from crystal forces.