Vinylene C-H stretch

The in-phase and quadrature spectra in the region between 1050 and 900 cm are shown in Figure 12.11. The peak at 1018 cm in the quadrature spectrum has been assigned to a vibration of the THT pendant group. The phase of the pendant group vibrations is different from that of the C—C ring stretches and the vinylene C—H stretch indicating that these vibrations are independent of the backbone vibrations. 

The in situ analysis of the precursor film during thermal conversion shows the gro vth of the vinylene (sp ) C-H stretching band at 3052 cm as... 

The synchronous and asynchronous plots of PPV in the CH region are as shown in Figures 21.17 and 21.18. The rapid change in phase across the vinylene C—H bend as shown in Figure 21.13a would imply the presence of several microstructural environments. The synchronous plot shows that the vinylene CH stretch can easily be resolved into two peaks at 3015 and 3030 cm The presence of peaks in the asynchronous plot at these two wavenumbers indicates that these two components are reorienting at different rates. 

The band at 1018 cm 1 is due to the presence of occulted oxygen in PE film (thickness, 22-24 pm). The bands at 452 and 456 cm"1 appear only for LDPE (thickness, 22-24 pm) which are attributed to the P (C=C-H). The disappearance of a small band at 888 cm"1 is possibly due to >CH2 out of plane deformation. This may be explained on the basis of evolution of hydrogen gas as a result of the degradation. The intensity of IR absorption bands at 1017, 1113, 1131, 1175, 1241 cm"1 is shown to increase with increasing irradiation dose. The intensity of the bands 1069 cm 1 (C-C stretching), 1287 cm 1 (OH bending), 1377 cm"1 (symmetrical deformation of CH3) (which are initially present in IR spectra of unirradiated films) increase with absorbed dose of radiation, whereas the intensity of the sharp band at 1456 cm"1 is not affected at all. The small band at 965 cm 1 is attributed to C-H out of plane deformation of trans-vinylene groups trans RCH=CHR). 

---