Modern Polymer Spect..

I."
0.9
0.8
Figure 2-34. FTlR 0.7
polarization spectra of
o, 0.6
an irradiated P8a 12 0
polyester (after 1000 s of 5 0.5
irradiation with the 488
0.4
nm line of an at-gon-ion p
laser at an intensity of a 0.3
800 mW/cm' I. The IR
0.2
beam was polarized
parallel and perpendicu- 0.1
......... parallel
- perpendicular
lar to the polarization 0.0
direction of the laser 3300 3000 2700 2400 2100 1800 1500 1200 900 600
beam.
Wavenumber I cm-1
Table 2-3. Band assignment. wavenumber position and structural origin of selected absorptions of
the polyester P8a12 (as = antisymmetric: s = symmetric; ar = aromatic: oop = out-of-plane).
Band assignment Wavenumber Structural origin
(cm-I)
c+~(CH?)
I's(CH2)
v(C-N)
I'(c=o)
1*(C=C),,
l'( C=C),,
t ~ CH2) (
is,,( C-0- Ar)
Various modes of coupled
COOR group vibrations
I*( N-Ar)
11, (C-0- Ar)
jjooP (CH I,,
;',(CH?)
2920
2851
1379
1733
1603 / 1583
1501
1403- 1355
1257
1201 . . . 1 I05
1141
1022
839
723
main chain / spacer
main chain / spacer
mesogen
main chain / (ester linkage)
mesogen
mesogen
main chain / spacer
mesogen / spacer
main chain / (ester linkage)
mesogen
mesogen / spacer
mesogen
main chain / spacer
the azobenzene moieties. the alignment of the spacer and the main chain can only
be induced by coupling effects. Investigations of polyesters with specifically deuterated
aliphatic sites in the spacer and main chain demonstrate, that the perpendicular
alignment of the acid-specific main chain relative to the laser polarization
direction is even better than the alignment of the side-chain spacer units 1001. Thus,
Figure 2-3% shows the region of the v(CH2) and v(CD2) polarization spectra of a
P6a12 polyester with a completely deuterated main chain (except the CH-group