Synthesis of Triptycene-Based Organosoluble, Thermally Stable, and Fluorescent Polymers: Efficient Host–Guest Complexation with Fullerene

Abstract

We report a facile synthesis of 2,6-diethynyltriptycene (DET) in high yield. Application of DET as monomer in polymer chemistry has been shown (for the first time) in syntheses of two novel polymers via Sonogashira cross-coupling reaction in high yield. The newly synthesized polymers were characterized by FT-IR, UV–vis absorption, and NMR spectroscopic techniques. The polymers prepared using DET have interesting properties such as high solubility in common organic solvents, high thermal stability [decomposition temperatures (T d) > 495 °C], and high char yield (greater than 81% at 900 °C). Additionally, polymers are fluorescent. Host–guest interaction between triptycene-based polymers and fullerene (C60) has been studied for the first time. Fluorescence quenching of our polymers by C60 has been used to study the extent of (polymer·C60) host–guest complex formation. Fluorescence quenching studies indicate binding constant for polymer·C60 complexation on the order of 105 M–1.

Triptycene‐based fluorescent polymers with pendant alkyl chains: interaction with fullerenes and morphology of thin films

“…S1 in File S1), the highest intensity absorption band was observed at λ max = 309 nm, attributed to π – π * transitions of the polymer backbone. The TPPEs were found to be fluorescent in nature even though two neighbouring triptycene units are bridged by 1,3‐diethynylarene bridges (less conjugating) instead of 1,4‐diethynylarene (more conjugating) as in an earlier report . Fluorescence excitation and emission spectra of the TPPEs ( λ ex = 312 and λ emi = 344 nm) were recorded in toluene solution (2 × 10 −7 mol L −1 ) at room temperature (Fig.…”

“…DET ( 1 ) is a triptycene‐based monomer, and was synthesized as reported earlier . Monomers 2 , 3 and 4 were the other three monomers utilized in the work reported here.…”

“…The internal free volume in triptycene‐based polymers renders these materials microporous in nature . In the case of triptycene‐based polymers that are fluorescent, the photoluminescent behaviour is attributed to diminished self‐quenching due to bulky triptycene units that reduce interchain π – π interactions …”

Altering the emission properties of conjugated polymers

“…When blended with electron acceptor fullerenes, these polymers exhibit a clear FL quenching (Fig. (a)), which suggests the formation of a polymer − fullerene complex most probably through π − π interactions between fullerene and electron donor triptycene . Such quenching is also observable in fluorescent images of a polymer solution when adding fullerene (Fig.…”

“…Note, in the context of OPVs, that the emission intensity of most CPs used in bulk heterojunction devices is modest. Exceptions include polymers based on 2,6‐diethynyltriptycene and aromatic dibromides that are fluorescent although the chromophores are discrete and non‐conjugated . When blended with electron acceptor fullerenes, these polymers exhibit a clear FL quenching (Fig.…”