Synthesis and characterization of novel luminescent polymers with alternate phenothiazine and divinylbenzene units

Novel luminescent polymers (P1 and P2) carrying alternate phenothiazine and divinylbenzene units were synthesized via the Wittig reaction. Absorption, fluorescence, and cyclic voltammetric methods were applied to investigate their optical and electrochemical properties. The photoluminescence (PL) maxima of P1 and P2 were 559 and 568 nm, respectively. Compared with reported hole-transport groups such as carbazole, alkyldiphenylamine, triphenylamine, and iminodibenzyl chromophores, phenothiazine moieties in P1 and P2 bathochromically shift the PL maxima and narrow the band gaps. Their relative PL efficiencies were about 0.5 and 0.3 in solution and in the film state, respectively. Moreover, highest occupied molecular orbitals of P1 (4.78 eV) and P2 (4.74 eV) were even higher than the work function of ITO electrode (4.8 eV). The threshold electric fields of the Al/P1 (or P2)/ITO device were about 1.52-1.63 · 10⁶ V/cm, which were smaller than 1.73 · 10⁶ V/cm of P3, consisting of alternate iminodibenzyl and divinylbenzene units.