Polarized Resonance Raman and FTIR Reflectance Spectroscopic Investigation of the Molecular Orientation in Industrial Poly(vinyl chloride) Specimens

Abstract

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 CH 2 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.

Carbon Nanotube Array/Polymer Core/Shell Structured Composites with High Dielectric Permittivity, Low Dielectric Loss, and Large Energy Density

“…It is generally believed that polarized Raman spectroscopy is a useful tool to characterize the changes in orientation of MWCNTs in the composite sheets with different volume fraction ( f ) of MWCNTs ( Figure ) 30–32. In the Raman spectrum of the MWCNTs (Figure 3a), the peak at 1590 cm −1 is a so‐called G‐band, which arises from the stretching of conjugated double bonds corresponding to sp 2 hybridization during the formation of the aryl nanotube bond.…”

“…In each group of Raman spectra, the VV curve represents the spectrum when the polarization of the incident laser is parallel to the nanofiber axis and the VH curve represents the spectrum when the polarization of the incident laser is perpendicular to the nanofiber axis 31. Normally, the degree of MWCNT alignment can be evaluated by the depolarization factor R , the ratio of the peak intensities of the G band in the two polarization directions, i.e., parallel (VV configuration) and perpendicular (VH configuration), to the fiber axis 30. Based on the data shown in Figure 3b, the marked increase in the R value can be observed from 2.29 to 6.82 with the increasing f of MWCNTs.…”

PVC Morphology

“…This technique is frequently used, but the method of interpreting results is still under dispute. 79 Density measurement is also a crystallinity indicator as it depends on the contribution of amorphous and crystalline phases. Also, not only the crystallinity of the sample affects IR absorption, but also the physical state, tacticity, history of the specimen, and so on.…”

Analytical Methods

“…[237][238][239] These two observations are essential findings from measurements of positron annihilation lifetime spectroscopy. 241 • determination of polyenes, 63,137,198,[242][243][244][245] • orientation, 246,247 • crystallinity and configuration, 248,248 • depth profiling, [250][251][252][253][254][255] • miscibility and interaction. 237 It increases above glass transition temperature from 0.10 to 0.18 nm 3 .…”