VIBRATIONAL CHARACTERIZATION OF AZOBENZENES, AZOXYBENZENES AND AZOAROMATIC AND AZOXYAROMATIC POLYETHERS

Raman and infrared spectra of a bisphenol-A-containing azoaromatic pol yether, a bisphenol-A-containing azoxyaromatic polyether and a bisphen ol-A-containing 2-hydroxyazoaromatic polyether were analyzed. Vibratio nal spectra were also collected for the corresponding model compounds 4,4'-(4-tert-butylphenoxy)azobenzene, 4,4'-(4-tert-butylphenoxy)azoxyb enzene and 4,4'-(4-tert-butylphenoxy)-2-hydroxyazobenzene. Comparisons with substituted azobenzenes and azoxybenzenes were used in assigning the spectra in the 1650-900 cm(-1) region. Assignments of the N=N str etch (1410-1390 cm(-1)) demonstrate that all of the compounds are in t he trans configuration. The azo bridge vibrations of the azoaromatic e thers are very similar to those of azobenzene. Different types of hydr ogen bonding are seen in the 2-hydroxyazoaromatic compounds. The polye ther has an OH stretch at 3355 cm(-1) which indicates a network of int ermolecular hydrogen bonds among the polymers. The 2-hydroxyazoaromati c model compound has no IR peak above 3100 cm(-1) and N=N, CO and CN s tretches which are shifted due to an intramolecular hydrogen band with the azo nitrogen. The N=N stretch of the azoxyaromatic ethers is at t he same wavenumber as in the azo compounds. Assignment of the N --> O stretch vibration is difficult because of mixing with other modes of t he azoxy bridge. (C) 1997 John Wiley & Sons, Ltd.