Synthesis of Novel Hyperbranched Polybenzo-Bisthiazole Amide with Donor⁻Acceptor (D-A) Architecture, High Fluorescent Quantum Yield and Large Stokes Shift.

Xiaobing Hu

doi:10.3390/polym9080304

Abstract

Two novel highly fluorescent hyperbranched polybenzobisthiazole amides with a donor–acceptor architecture and large Stokes shift were rationally designed and synthesized. The chemical structures of the prepared hyperbranched polymers were characterized using Fourier Transform Infrared Spectroscopy (FTIR) analysis, Hydrogen Nuclear Magnetic Resonance (1H-NMR) analysis, and Gel Permeation Chromatography (GPC) analysis. These two polymers were soluble in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and their DMSO and DMF solutions emitted strong green light (517–537 nm) with high quantum yields (QYs) and large Stokes shifts. Their relative fluorescence QYs in the DMSO solution were calculated as 77.75% and 81.14% with the Stokes shifts of 137 nm (0.86 eV) and 149 nm (0.92 eV) for HP–COOH and HP–NH2, respectively, using quinine sulfate as the standard. In the DMF solution, the QYs of HP–COOH and HP–NH2 were calculated as 104.65% and 118.72%, with the Stokes shifts of 128 nm (0.79 eV) and 147 nm (0.87 eV), respectively. Their films mainly emitted strong blue light with the maximum emission wavelengths of 436 nm and 480 nm for HP–COOH and HP–NH2, respectively. The Stokes shifts for HP–COOH and HP–NH2 films were 131 nm (0.42 eV) and 179 nm (0.86 eV), respectively. They are promising candidates for luminescent solar concentrators and blue light emitting materials.

Highlights

In the DMF solution, the quantum yields (QYs) of HP–COOH and HP–NH2 were calculated as 104.65% and 118.72%, with the Stokes shifts of 128 nm (0.79 eV) and 147 nm (0.87 eV), respectively
For HP–COOH and HP–NH2, the 1,3,5-trisubstitutedphenyl benzene (1,3,5-TPB) moiety acts as the branching point
All of the possible molecule structures of the obtained polymers (HP–COOH and HP–NH2 ) are shown in Scheme 1 with a focus on the functional groups bonded to the 1,3,5-TPB moiety

Summary

Introduction

Over the past few decades, hyperbranched polymers have drawn continuous and considerable attention because of their unique molecular architecture, improved physical and chemical properties, and their broad range of applications, such as fluorescent probes [1,2,3,4,5], polymer coatings [6,7], Separation materials [8], drug or biomolecule carrier materials [9,10,11,12,13,14,15,16], and in optoelectronic materials and devices [17,18,19,20,21,22,23,24,25,26]. Compared to linear polymers, hyperbranched polymers have the obvious advantages of high solubility, little chain entanglement, low viscosity, good processability, tunable light emission, low crystallinity, and controllable thin film morphology [27,28]. They have highly branched architecture, and large numbers of functional terminal groups and nanoscale cavities, and they are superior to their dendritic counterparts because of their convenient “one-pot” synthesis and their potential for large-scale production [29]. For the ABn strategy, gelation is easy to avoid in theory, the monomers are usually difficult to synthesize, because the molecules have two different reactive groups and they can undergo self-polymerization in some cases. The second strategy, A2 + Bn , has certain merits, Polymers 2017, 9, 304; doi:10.3390/polym9080304 www.mdpi.com/journal/polymers

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Conclusion