Protonation Effect of Polybenzoxazole: Experimental Evidence.

In order to investigate the protonation effect of polybenzoxazole, a type of soluble thiophene-based polybenzoxazole (PBOP-Th) is synthesized and characterized by the FTIR, 1H-NMR, elemental analysis, thermogravimetric analysis (TGA), UV-Vis and photoluminescence (PL) spectra. Another polymer aminophenols-based polybenzoxazole (PBOP-Ph) was also synthesized as reference polymer. Unlike usual polybenzoxazoles such as poly(p-phenylenebenzobisoxazole) (PBO) and poly(2,5-thienylbenzobisoxazole) (PBOT), PBOP-Th and PBO-Ph have greatly enhanced solubility due to the introduction of isopropylidene and/or thiophene cycle. The effect of protonation on photophysical properties of polybenzoxazoles is studied by an experimental method for the first time. The 30 nm red shift on the UV-Vis and PL spectra of polymer is observed in methanesulfonic acid (MSA) solution compared with that of polymer in neutral N,N-dimethyl fomamide (DMF) solution, which is believed to be due to the protonation effect. [ABSTRACT FROM AUTHOR]