Fluorescent Polystyrene Films for the Detection of Volatile Organic Compounds Using the Twisted Intramolecular Charge Transfer Mechanism

Abstract

Thin films of styrene copolymers containing fluorescent molecular rotors were demonstrated to be strongly sensitive to volatile organic compounds (VOCs). Styrene copolymers of 2-[4-vinyl(1,1′-biphenyl)-4′-yl]-cyanovinyljulolidine (JCBF) were prepared with different P(STY-co-JCBF)(m) compositions (m% = 0.10–1.00) and molecular weights of about 12,000 g/mol. Methanol solutions of JCBF were not emissive due to the formation of the typical twisted intramolecular charge transfer (TICT) state at low viscosity regime, which formation was effectively hampered by adding progressive amounts of glycerol. The sensing performances of the spin-coated copolymer films (thickness of about 4 µm) demonstrated significant vapochromism when exposed to VOCs characterized by high vapour pressure and favourable interaction with the polymer matrix such as tetrahydrofurane (THF), CHCl3 and CH2Cl2. The vapochromic response was also reversible and reproducible after successive exposure cycles, whereas the fluorescence variation scaled linearly with VOC concentration, thus suggesting future applications as VOC optical sensors.

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

“…By taking advantage of the covalent anchorage of the fluorescent JCBF co‐unit within the terpolymer backbone, its self‐associative behavior in water was studied as a function of temperature by monitoring the fluorescence response of the JCBF probe. 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.…”

“…2‐Cyano‐2‐[4‐vinyl(1,1′‐biphenyl)‐4′‐yl]vinyljulolidine (JCBF) was synthesized according to a reported procedure …”

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.…”