Synthesis and characterization of new cardo poly(bisbenzoxazole)s containing fluorenylidene unit

A series of poly(bisbenzoxazole)s (PBOs V) containing fluorenylidene unit are prepared from 9,9-bis(3-amino-4-hydroxyphenyl)fluorene (BAHPF) and various aromatic or alkene diacids by direct polycondensation. These polymers exhibit improved solubility and good thermal stability. The decomposition temperatures at 10% weight loss of them are above 500 °C. X-ray diffractograms of PBOs V1–5 show that all of them are amorphous. The maximum absorption wavelengths of PBOs V1–5 are blue or red shifted relative to poly(p-phenylene-2,6-benzobisoxazole) (PBO). The bandgaps of PBOs V1–5 are in the range of 2.48–2.98 eV, which widen the tunable range of the optical bandgap. The results of photoluminescence (PL) emission spectra indicate the energy transportation has happened between the fluorenylidene and benzoxazole ring. The emission wavelengths of PBOs V1–5 are blue shifted in contrast to PBO and the emission wavelengths of them are in the region of blue or green light, respectively. The PL quantum yields of them are improved due to the introduction of fluorenylidene group. The results of EPR studies show the intrinsic paramagnetic defects in this class of polymers.