Hyperbranched copolymer based photoluminescent vesicular probe conjugated with tetraphenylethene: Synthesis, aggregation-induced emission and explosive detection

A carboxyl functionalized hyperbranched polymer, poly(3-ethyl-3-oxetanemethanol)-star-poly(ethylene oxide) (HSP-COOH) was subjected to addition reaction with tetraphenylethene (TPE) containing thioethanol (i.e. 2-((4-(1,2,2 triphenylvinyl)phenethyl)thio)ethanol (TPE-OH) to afford HSP-TPE copolymer with high yields. The TPE grafted hyperbranched copolymer forms homogeneous solution in common organic solvents such as THF. In aqueous solution, the copolymer self-assemble to form aggregates. The aggregates display maximum photoluminescence (PL) in THF/water (3:7 v/v) mixture. The introduction of TPE units into polymer makes it highly sensitive probe for picric acid (PA) with detection limit as low as 20 ppb via aggregation induced emission. The PL was effectively quenched by possible π-π interactions between TPE units of HSP-TPE and hydroxyl containing phenolic acid. The quenching efficiency significantly increased nonlinearly at higher quencher concentration. The present study offers details for design and synthesis of new hyperbranched polymeric fluorescent vesicle probe with high sensitivity.