BODIPY based hyperbranched conjugated polymers for detecting organic vapors†
A series of A2B3 and A2B4 type hyperbranched polymers (HP1–HP3) based on 4,4′-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) was synthesized via Sonogashira cross coupling polymerization reactions. The target polymers were fully characterized with molecular weights (Mn) of 10 000 to 25 000 g mol−1 and were soluble in common organic solvents. The polymers showed red shifts in absorption maxima (570 nm to 630 nm) in the solution state compared to that of BODIPY monomers (540 nm). Particularly, the absorption studies done in solution suggest strong interactions between HP2 and toluene with observed red shifts in absorption maxima (20 nm) and emission maxima (11 nm) when the solvent was changed from chloroform to toluene for the optical measurements. All polymers were coated on quartz crystal microbalance (QCM) electrodes for sensing organic vapors. Among all polymers tested, HP2 showed high sensitivity towards benzene and toluene vapors. In addition, the hyperbranched polymer HP2 has higher sensitivity for toluene over benzene compared to linear BODIPY copolymers. Such sensitive polymers are useful for the development of potential sensors for aromatic molecules.