By using characteristics of carboxyl groups and azo chromophores

the pH sensitivity and thermo-optic properties of the side-chain azo polyelectrolytes were studied. A chromophore molecule containing azobenzene

4-(4′-nitrophenylazo)phenol was synthesized from 4-nitroaniline

sodium nitrite and phenol via diazo-coupling reaction. A side-chain azo polyelectrolyte was obtained from the chromophore molecule

epoxy chloropropane and αmethacrylic acid by free radical polymerization. The chemical structures of azo polyelectrolytes were characterized by FTIR

UV-Vis spectroscopy and 1HNMR. The thermal properties were characterized using differential scanning calorimetry (DSC)

and the glass transition temperature (Tg) 189.8℃ showed that the azo polyelectrolyte had high thermal stability. Influences of different pH values on the UV-Vis absorption spectra of the azo polyelectrolyte were studied. The results showed that the UV-Vis absorption spectra of the azo polyelectrolyte changed with the pH value and the azo polyelectrolyte had high pH sensitivity. The measurements of refractive index (n) and thermooptic coefficient (dn/dT) of the azo polyelectrolyte were demonstrated at 650 nm and TM mode by using the attenuated total reflection (ATR) technique. The thermo-optic coefficient (dn/dT) was -1.92479×10-4℃-1

which was one order of magnitude larger than that of inorganic glasses such as zinc silicate glass (5.5×10-6℃-1)

borosilicate glass (4.1×10-6℃-1) and was larger than the organic material such as polystyrene (1.23×10-4℃-1) and PMMA (1.20×10-4℃-1). These results indicate that the material may be provided to develop the new digital thermo-optic switch with low drive power.