Distyrylbenzene-based segmented conjugated polymers: Synthesis, thin film morphology and chemosensing of hydrophobic and hydrophilic nitroaromatics in aqueous media

Abstract

Two new segmented conjugated polymers bearing distyrylbenzene chromophoric units and their model compounds were synthesized. The tendency of the model compounds to form H-and J-type aggregates in the amorphous matrix was greatly diminished by the twisted polymeric architecture. Fluorescence anisotropy measurements indicated good exciton mobilities in condensed phase. Fluorescence quenching by nitroaromatic aqueous solutions was fast, complete, selective and reversible pointing to a rapid diffusion of analytes into the films. The quenching response to nitrophenols was superior to that against nitrotoluenes. The increase of the electron-donating capabilities by diethoxy-substitution was detrimental to the amorphous morphology and it did not increase sensitivity to NACs. Quenching efficiencies of polymers were not modified when MeOH was used instead of water. The solubility parameter distances, R a . indicate that the sensing materials show higher responses when their affinity with the analytes is lower. This observation could help in the designing of fluorescent sensors.

Fluorescent Amorphous Distyrylnaphthalene-Based Polymers: Synthesis, Characterization and Thin-Film Nanomolar Sensing of Nitroaromatics in Water

“…The reaction of the dibromides with triethylphosphite afforded the bisphosphonates 1a and 1b [28]. Aldehyde 2 and dialdehyde 3 were prepared according to the literature [13]. The details of the synthesis and characterization of the synthetic precursors, monomer, model compounds M14 and M26 and the polymers P14 and P26 are presented in Supplementary Materials.…”

“…In order to obtain amorphous morphologies that could favor diffusion of the analyte from the aqueous solution into the polymeric film, we knitted semi-rigid fluorophores with isopropylene units, which confer a highly twisted nature to the main chain. We found that thin films of these disordered assemblies of fluorophores proved to be very sensitive towards NACs in aqueous media [12,13]. Indeed, we and many others have found that different fluorescent materials [14,15,16,17,18,19,20,21,22,23,24], despite their huge disparity in chemical structure, are very responsive in aqueous media towards picric acid (PA) and show no, or a small, responses to trinitrotoluene (TNT) and related nitrotoluenes.…”

Supramolecular Luminescent Sensors

“…In another example, distyrylbenzene conjugated segments were linked by isopropylene spacers to generate a segmented conjugated polymer that responded to nitroaromatic analytes with a strong decrease in fluorescence (Figure a) . Of note, distyrylbenzene as a chromophore has been reported as a key component of luminescent amine sensors and as part of proton sensing for pH detection schemes .…”

Conjugated polymers containing tetraphenylethylene in the backbones and side-chains for highly sensitive TNT detection

“…These values are among the best in the published literature. 23,29,49,50 The response of dispersed PTPA1-TPE nanoaggregates towards other aromatic analytes have been also tested, as shown in Fig. 6.…”