A series of linear aromatic polyethers containing triazole units were synthesized via the direct click reaction of dibromide and bisethynyl compounds in the presence of sodium azide as one pot reaction. The structures of polymers were approved by using IR and 1H NMR techniques. The solubility experiments showed that polymers have good solubility in polar aprotic solvents such as DMSO, DMF, and NMP at higher temperatures. Thermal stability of the polymers was measured using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) which indicated that they possessed good thermal stability (
Poly(arylene ether)s (PAEs) are known as an important class of the high-performance polymeric materials which consist of aromatic rings and ether linkages [
Recent innovations in synthetic methodology have improved polymer synthesis, enabling the custom design of a large variety of macromolecular architectures under incorporation of desired functional units [
To date, the most popular reaction that satisfied these features is the 1,3-dipolar cycloaddition, also known as Huisgen cycloaddition, between an azide and a terminal alkyne which affords the triazole moiety [
Although, the applications of click reaction in materials science are especially interesting, most of them were focused on the preparation of dendronized polymers [
In this paper, we wish to describe the synthesis and characterization of a novel class of linear aromatic and aliphatic polyethers such as poly(ether ketone)s, poly(ether sulfone)s, and fluorinated poly ether containing triazole units in the backbone via the in situ click reaction of bisethynyl and dibromide compounds in the presence of sodium azide as a tricomponents reaction.
Acetone was dried over CaH2 and distillated before use. Other reagents or materials were used as received. The chemicals used in this experiment were purchased from Merck (Germany).
Melting points were measured by an Electrothermal 9100 apparatus. 1H NMR spectra were recorded on a Bruker DRX-400. IR spectra were recorded on a Perkin Elmer FT-IR- 1710 spectrophotometer. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were recorded on a thermal science PLSTA 1500 system under nitrogen atmosphere at a heating rate of 10°C min−1. Inherent viscosity at a concentration of 0.5 g/dL was measured with an Ubbelohde suspended-level viscometer at 25°C in DMSO solution. X-ray diffraction (XRD) patterns were obtained at room temperature on a Rigaku D/Max-2550 powder diffractometer with a scanning speed of 5° min−1, and the patterns were recorded in the
Bisphenol (0.05 mol), potassium carbonate (0.15 mol), dry acetone (50 mL), and propargyl bromide (0.125 mol) were mixed in a round bottom flask equipped with a condenser and a heater stirrer. Then the mixture was kept at 80°C overnight. On completion of the reaction, the solvent was evaporated and the product was washed with 5% K2CO3 aq. and deionized water several times. The crude product was purified by column chromatography on silica gel using n-hexane/ethyl acetate (4 : 1) as eluent to give
Synthesis of bis propargyl ethers.
In a 25 mL flask, to a solution of bisethynyl compounds (0.50 mmol), dibromide (146 mg, 0.50 mmol) and sodium azide (71.5 mg, 1.1 mmol) in DMF (10 mL), was added a suspension of CuCl (9.85 mg, 20 mol %) in H2O (2 mL) in dropwise. Then NEt3 was added gradually until color of mixture changes from brown to light green. The reaction mixture was stirred at room temperature for 24 h. The reaction mixture was diluted by water (20 mL) and then concentrated ammonia (5 mL) was added and stirred for another 1 h. The mixture was filtered and the resulting solid material was washed with H2O, methanol, and THF. Finally, the obtained polymer was further purified using continuous extraction by soxhlet in THF.
Since triazole ring is chemically inert toward oxidation, reduction, and hydrolysis conditions and has an intermediate polarity [
Synthesis of poly(triazole ether)s.
IR of
400 MHz 1H NMR of
The corresponding data of GPC analysis in DMF for polymers were showed in Table
Molecular weights and distributions of polymers.
Polymers |
|
|
|
|
---|---|---|---|---|
|
23,100 | 29,800 | 1.29 | 0.62 |
|
21,000 | 32,200 | 1.53 | 0.58 |
|
21,300 | 32,800 | 1.54 | 0.55 |
|
24,800 | 27,000 | 1.09 | 0.63 |
|
19,100 | 30,900 | 1.62 | 0.45 |
|
17,300 | 29,100 | 1.68 | 0.42 |
|
20,500 | 27,500 | 1.34 | 0.49 |
|
22,400 | 27,300 | 1.22 | 0.58 |
The solubility of polymers was quantitatively determined in common organic solvents by dissolving 5.0 mg of solid polymers in 1.0 mL of solvents. In the solubility experiments, it was found that these polymers were completely insoluble in MeOH, THF, EtOAc, and toluene at room and high temperatures. But polymers showed low solubility in DMSO, DMF, and NMP at room temperature and good solubility at higher temperatures.
Thermal stabilities of
Thermal properties of polymers.
Polymers |
|
|
|
Char yield (%) |
|
---|---|---|---|---|---|
|
249.6 | 321.4 | 499.5 | 46 | 210 |
|
274.2 | 313.8 | 556.7 | 48.3 | 260 |
|
271.3 | 309 | — | 54.46 | 220 |
|
302.2 | 310.9 | 558.8 | 44.3 | 212.5 |
|
327.1 | 345.6 | 390.9 | 25.6 | 191.7 |
|
287.4 | 319.1 | 410.2 | 32.9 | 196.7 |
|
261.7 | 316.05 | 469.64 | 42.7 | 208.3 |
|
175.2 | 297.5 | 370.8 | 18.7 | 196.8 |
Thermogravimetric analysis under N2 atmosphere and heating rate of 10°C/min.
Differential scanning calorimetric under N2 gas with heating rate of 10°C/min.
The photophysical properties of the
UV-vis absorption spectra of
In order to further consider the crystallinity of these series of polymers, all polyether triazoles were characterized by X-ray diffractograms. The X-ray diffractogram curves of polymers were shown in Figure
X-ray diffraction (XRD) patterns at room temperature on a powder diffractometer.
In this work, convenient tricomponent click polymerizations of dialkynes containing ether linkages and dibromides were achieved in the presence of sodium azide to synthesize various polyethers (
The financial supports by Research Council of Mazandaran University are gratefully acknowledged.