Polythiosemicarbazones by Condensation of Dithiosemicarbazides and Dialdehydes

Abstract

An easy access to thermoplastic polythiosemicarbazones (polyTSCs) is presented by condensation of dithiosemicarbazides and aromatic dialdehydes, yielding eight polyTSCs and five co-polyTSCs, exhibiting M ns up to 38 kDa in good yields (58–93%). The polymerization proceeds at room temperature and is typically finished after 2–3 h. The monomer scope was investigated, revealing broad moiety tolerance (aliphatic, cyclic, benzylic, and aromatic groups). Full characterization was performed by proton and carbon NMR spectroscopy, IR spectroscopy, and size exclusion chromatography, confirming the anticipated chemical structure of polyTSCs. Thermal analysis of the polymers showed degradation starting at ∼200 °C by decomposition of the TSC function. Glass transitions were only observed for polymers derived from rigid monomers (162–198 °C). Further versatility of the reaction was underlined by the synthesis of five copolymers using different dithiosemicarbazide monomers.

Removal of Transition-Metal Ions by Metal-Complexing Polythiosemicarbazone Membranes

“…This result was reasonable because the pTSC group exhibits an acidic proton attached to the hydrazide moiety of the TSC group (the chemical shift of the respective proton in a 1 H NMR spectrum in DMSO-d 6 was 11.50 ppm). 34 A clear connection between the pK a value of TSCs and their deep-field signal of the NH-hydrazide proton has been reported by Mendes et al 39 The negative charge would mean that the membrane can retain co-ions via the Donnan exclusion mechanism, resulting in higher retentions for Na 2 SO 4 . However, that was not the case and no retentions were found for any of the salts tested (NaCl, Na 2 SO 4 , and MgCl 2 ).…”

“…This process was repeated three times. The polymer was obtained after drying at 100 °C and 12 mbar for at least 20 h. The pTSC product was obtained as yellow polymer balls (1.25 g) in a yield of 98% containing less than 1 wt % DMSO …”

“…The polymer polythiosemicarbazone (pTSC) was synthesized according to the protocol mentioned in our earlier work. 34 Briefly, N,N′-(dodecane-1,12-diyl) bis(hydrazinecarbothioamide) (1.00 g, 2.87 mol, 1.00 equiv) and terephthaldehyde (385 mg, 2.87 mmol, 1.00 equiv) were added to 1.9 mL of DMSO and the reaction was stirred at room temperature for 2 h. Subsequently, 2 mL of NMP was added to the reaction mixture to solubilize the polymer using a sonification bath (50 °C, 80 kHz). Precipitation was performed by the dropwise addition of the polymer solution to 400 mL of cold water.…”

“…In this work, we propose polythiosemicarbazone (pTSC) as a metal-complexing polymer to fabricate membranes for transition-metal ion removal from aqueous streams. The structure of the investigated pTSC polymer is depicted in Figure , which contains two complexing thiosemicarbazone (TSC) ligands per repeat unit that forms complexes with transition-metal ions. − Herein, we use the recently introduced pTSCs obtained by feasible polycondensation of dithiosemicarbazones and dialdehydes , to prepare polymeric pTSC membranes for the first time and demonstrate their transition ion removal performance. The polymer was first dissolved in either dimethyl sulfoxide (DMSO) or 1-methyl-2-pyrrolidinone (NMP) to obtain casting solutions, which were transformed into solid membranes by immersion in a water bath.…”