Vapochromic features of new luminogens based on julolidine-containing styrene copolymers

Abstract

We report on vapochromic films suitable for detecting volatile organic compounds (VOCs), based on new polystyrene copolymers containing julolidine fluorescent molecular rotors (JCAEM). Poly(styrene-co-hydroxyethylmethacrylate) copolymers functionalized with cyanovinyl-julolidine moieties of different compositions were prepared, (P(STY-co-JCAEM)(m) with m = 0.06–0.61). The sensing performance of the spin-coated copolymer films demonstrated significant vapochromism when exposed to VOCs characterized by high vapour pressure and a favourable interaction with the polymer matrix, such as Et2O and CH2Cl2. It is worth mentioning that the fluorescence decrease rate was 7 times faster than that of previously investigated julolidine-based fluorescent molecular rotors dispersed in PS films. This phenomenon was attributed to the better control of the JCAEM moiety distribution in the polymer matrix conferred by the covalent approach, combined with a minimal film thickness of 4 microns. These factors, in concert, strongly accelerate the deactivation pathways of the JCAEM units in the presence of VOCs which interact well. Overall, the present results support the use of julolidine-enriched styrene copolymers as effective chromogenic materials suitable for the fast detection of VOCs.

The self‐assembly over nano‐ to submicro‐length scales in water of a fluorescent julolidine‐labeled amphiphilic random terpolymer

“…S3), with an associated negligible quantum yield ( Φ = 5.11·10 −3 ). This value was slightly higher than that of the corresponding monomer, owing to the enhanced steric hindrance of the JCBF moiety covalently linked to the macromolecular chain …”

“…An in‐depth characterization of the JCBF monomer was recently published . Briefly, UV–vis spectra of JCBF in chloroform solutions showed a characteristic absorption peak at around 407 nm ( ɛ = 21,500 M −1 ·cm −1 ), typical of cyanovinyl julolidine derivatives, and a second absorption peak at about 290 nm, due to the π → π * electronic transition of the biphenyl moiety. The fluorescence emission maximum was at around 500 nm ( λ exc = 410 nm) with a negligible fluorescence quantum yield ( Φ = 2.11·10 −3 ) due to the preferential formation, in low viscosity media, of the radiationless TICT excited state.…”

Vapochromic polyketone films based on aggregation‐induced enhanced emission

“…Emission from the sample is then directed back through the bundle into the collection port of the sample compartment. The emission response of the films towards vapors of VOCs was tested by exposing the sample held by a steel tripod in a 50‐mL beaker closed by a pierced aluminum foil lid, to different concentrations of various organic solvents of different vapor pressure and interaction with PK …”

“…In addition, pressing issues in global security are triggering the design of novel chromogenic compounds aimed at detecting environment changes with optical responses even more effective. For example, thermoplastic indicators containing fluorophore sensitive to viscosity changes have been used with success for the detection of VOCs . Notably, plastic films containing moderate amounts of the chromophoric probe (<0.1 wt%) display fluorescence variations upon the exposure to well‐interacting VOCs due to an induced plasticization of the continuous polymer phase .…”

“…For example, thermoplastic indicators containing fluorophore sensitive to viscosity changes have been used with success for the detection of VOCs . Notably, plastic films containing moderate amounts of the chromophoric probe (<0.1 wt%) display fluorescence variations upon the exposure to well‐interacting VOCs due to an induced plasticization of the continuous polymer phase . Plasticization means also viscosity decreasing, thus allowing the dispersed fluorophores to aggregate together upon a certain concentration threshold, which in turn causes evident color changes.…”