Modern Polymer Spect..

3.19 A Worked Example 185
19 5°C
215°C
28°C
Figure 3-48. Temperature dependence of
the infrared spectrum of a-nonadecane
in the CW2 rocking region showing that
the crystal field doublets coalesce into
singlets at the orthorhombic 4 c( phase
transitioiis indicating the existence of 780 760 740 720 700
‘single chains’.
v cm-1
(a) At T, the band progression of the P modes which shows factor group splitting
at lower temperature loses all the splitting, but remains as prominent feature in
the IR spectrum until T, (Figure 3-48).
(b) The progression of the P modes disappears at T,, and is replaced by a broad
band near 722 crn-l.