Characterization of orientation in polymers by polarized ir radiation.
The two-phase fringed micelle model for relating ir dichroic effects to polymer structure was discussed and used exptl. on drawn films of poly(+-)-(b-aminobutyric acid) (I) [52339-73-8]. The dichroic ratio (E) of the N-H stretching vibration bond at 3285 cm-1 for I was 5-10% lower (indicating a higher extent of perpendicularity to the draw direction) than the R value of the Amide I bond at 1645 cm-1. Although the absorption of the bond at 1645 cm-1 is generally attributed to the C:O stretching vibration, the higher dichroic ratio R indicates that the transition moment of this bond is displaced .apprx.15 Deg from the C:O bond direction, which is nearly perpendicular to the chain axis. This displacement was explained by the mech. interaction of the C:O and C-N stretching vibrations and an addnl. oscillating dipole moment in the N-O direction of the resonance structure of amide group, thus demonstrating the use of polarized light as an aid in the assignment of ir bonds.
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