Synthesis of Fully Soluble Azomethine-Bridged Ladder-Type Poly(p-phenylenes) by Bischler-Napieralski Reaction

The synthesis of fully soluble azomethine-bridged ladder-type poly(p-phenylenes) by Bischler-Napieralski reaction was investigated. 60 wt % NaH (0.96 g, 24 mmol) and 1-bromododecane (3.26 g, 13.1 mmol) were added into the solution of 2,7-dibromo-9H-carbazole, (3.27 g, 10.1 mmol), in DMF (40 mL). The mixture was stirred overnight at room temperature. The mixture was poured into water (200 mL), then the aqueous layer was extracted with diethyl ether, and the combined organic layers were dried over Na2SO4 and evaporated to dryness. The newly developed synthetic method allows the preparation of ladder polymers with good structural perfection. The synthesized ladder polymers were of high molecular weight and highly soluble in common organic solvents. The photophysical properties indicated that the phenanthridine-containing ladder-type polymers are effective pH sensor materials.