Abstract
Poly(2,5-dimercapto-1,3,4-thiadiazole) (PBT) nanosheets were synthesized by chemical oxidative synthesis under mild conditions. The media, oxidant species, monomer concentrations, oxidant/monomer molar ratio, and temperature were optimized to achieve higher yields and better performance. The molecular structure, morphology, and properties of the nanosheets were analyzed by Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis), and fluorescence spectroscopies, wide-angle X-ray diffraction (WAXD), matrix-assisted laser desorption/ionization/time-of-flight (MALDI-TOF) mass spectrometry, X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), and simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC). It was found that the polymerization of 2,5-dimercapto-1,3,4-thiadiazole occurs via dehydrogenation coupling between two mercapto groups to form the –S–S– bond. PBTs show the highest polymerization yield of up to 98.47% and form uniform nanosheets with a thickness of 89~367 nm. poly(2,5-dimercapto-1,3,4-thiadiazole) polymers (PBTs) exhibit good chemical resistance, high thermostability, interesting blue-light emitting fluorescence, and wonderful heavy metal ion adsorption properties. Particularly, the PBT nanosheets having a unique synergic combination of three kinds of active –S–, –SH, and =N– groups with a moderate specific area of 15.85 m2 g−1 exhibit an ultra-rapid initial adsorption rate of 10,653 mg g−1 h−1 and an ultrahigh adsorption capacity of up to 680.01 mg g−1 for mercury ion, becoming ultrafast chelate nanosorbents with a high adsorption capacity. With these impressive properties, PBT nanosheets are very promising materials in the fields of water treatment, sensors, and electrodes.
Highlights
Over the past two decades, heterocyclic aromatic polymers have attracted a great deal of attention from both academic and industrial communities
The differential scanning calorimetry (DSC) plots reveal that PBT polymers synthesized with I2 and H2 O2 display an endothermic peak at 176 ◦ C and 216 ◦ C, respectively, probably originating from the melting of a small part of the BT oligomers [32], since they show no weight loss at the transition temperature
Unique poly(2,5-dimercapto-1,3,4-thiadiazole) (PBT) nanosheets have been successfully synthesized through a simple chemical oxidative polymerization under environmentally friendly conditions
Summary
Over the past two decades, heterocyclic aromatic polymers have attracted a great deal of attention from both academic and industrial communities. Traditional heterocyclic aromatic polymers, such as polypyrrole and polythiophene, have been synthesized generally by either the electrochemical or chemical oxidative polymerization method [1,2,3]. It is desirable to synthesize poly(2,5-dimercapto-1,3,4-thiadiazole) (PBT) as a promising adsorbent for heavy metal ions. Qin, and coworkers [20,21,22] have attempted to synthesize a 1,3,4-thiadiazole ring containing polymers by using the chemical oxidative method, but merely obtained metal coordination polymers instead of genuine polymers like polypyrrole and polythiophene. The discharge of sewage containing heavy metal ions, especially mercury ions and lead ions, can do irreversible harm to the environment and human beings [24,25,26]. The adsorption performance for heavy metal ions of the polymer was studied in detail
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