Polarized resonance Raman and FTIR reflectance spectroscopic investigation of the molecular orientation in industrial poly(vinyl chloride) specimens

The molecular orientation of uniaxially drawn commercial poly(vinyl chloride), PVC, specimens has been investigated by polarized Fourier transform infrared (FTIR) in the specular reflectance mode and by resonance Raman scattering in various combinations of sample orientation, scattering configuration and polarization geometry. The orientation was examined as a function of the specimen draw ratio. The Kramers-Kronig transformation has been used to obtain infrared absorption spectra from the FTIR reflectance data; the orientation was determined by the dichroic ratio of the C-Cl stretching and CH2 rocking modes of PVC. The resonance Raman spectra of polyene segments that result from partial thermal degradation/dehydrochlorination of PVC during processing have been utilized in order to determine the parameters of the orientation distribution function. The all-trans conjugated polyene sequences formed during degradation are considered as rodlike segments in the polymer backbone and are used as indicators of orientation within the amorphous-like polymer phase. As far as the trends are concerned, data analysis showed good agreement between FTIR and Raman results regarding the induced molecular orientation in industrial PVC specimens.