The coordination may also be confirmed by the IR spectrum. The absorption of the C=S moieties in OTZnS was observed at 1,160 cm−1, which were shifted from the absorption of OTSH at 1,165 cm−1. The low-wavenumber shift indicates the decrease in the sp 2 character of the C=S moieties by coordination.

Because other TZnS polymers were almost insoluble, their structures were elucidated by IR spectroscopy. The IR absorptions of the S-H bonds were not observable in all the IR spectra. Low-wavenumber shifts of the IR absorptions of the C=S bonds were observed selleckchem in all the spectra. These data support the formation of the identical zinc thiolate structures. Figure 3 1 H-NMR spectrum of OTZnS (400 MHz, CDCl 3 /CF 3 COOH ( v / v = 5:1)). The assignment of the signals (a-h) is indicated on the structure. Figure 4 13 C-NMR spectrum of OTSH and OTZnS (100 MHz, CDCl 3 /CF 3 COOH ( v / v = 5:1)). The assignment of the signals (a-i) is indicated on the structures. Figure 5 IR spectra of OTSH and OTZnS (KBr disks). The polycondensation of OTSH and Zn(OAc)2 was conducted under various

conditions (Table 2). The effect of temperature was examined at 40°C to 80°C (runs 1 to 3). The yields were identical when the polymerization was conducted at 60°C and 80°C, but the yield decreased at 40°C, probably by the insufficient reactivity. The effect of concentration was not considerable. When the polycondensation was conducted in dioxane (12.5 to 37.5 L amounts toward 1 mol of https://www.selleckchem.com/products/p5091-p005091.html OTSH), both the yields and the molecular weights were almost identical, but the higher concentration slightly increased the M w/M n by the increase in the fraction with higher molecular Amylase weight (run 4). The increase of the high molecular weight fraction is attributable to the increased frequency of intermolecular coupling in this polycondensation of trifunctional and difunctional monomers. The polycondensation at 60°C under appropriately dilute concentration was proved to be the suitable conditions among examined. Although we tried polycondensation in the presence of tertiary amines to

accelerate the condensation, the yield was not increased and the structure of the product became complex, probably by the undesired oxidative coupling of the thiol moieties. The see more hydrodynamic radius of the polymers determined by DLS indicated the nano-sized structure. Table 2 Polycondensation of OTSH and Zn(OAc) 2 under various conditions Run Temperature (°C) Dioxane (L/molOTSH) Yield (%)a M n(M w/M n)b R h(nm)c 1 40 25 31 5,800 (1.4) 28 2 60 25 46 7,400 (1.4) 82 3 80 25 43 7,700 (1.6) 85 4 60 12.5 46 8,300 (2.1) 83 5 60 37.5 42 7,000 (1.6) 61 Conditions: OTSH = 0.200 mmol, Zn(OAc)2 = 0.300 mmol, 24 h, N2. aIsolated yield after precipitation into methanol. bEstimated by GPC (THF, polystyrene standards). cHydrodynamic radius determined by DLS (THF, 25°C, 1.3 g/L).