Synthesis and degradation kinetics of a novel polyester containing bithiazole rings
Highlights
► A novel Schiff base type polyester was synthesized and characterized by FTIR spectroscopy, elemental analysis, and X-ray diffraction spectroscopy. ► Thermal degradation of the polyester in nitrogen has been studied at several heating rates by thermogravimetric analysis. ► The activation energies were calculated by different methods. And the possible conversation function was estimated. ► The life time estimates for the polyester can be determined and the results demonstrate that the polymer possesses good thermal resistance.
Introduction
The field of organometallic polymers is attracting the interest of researchers due to the fact that metal-containing polymers may possess more special properties than conventional organic polymers. In 1998, Hoffmann et al. [1] proposed that polymers built from sulphur, carbon, and nitrogen-containing five-membered rings would theoretically display magnetic ordering. Heteroaromatic cyclic complexes formed from suitable metals and organic ligands are some of the best candidates for organic magnetic materials. More recently, it was found that aromatic heterocyclic polymers containing bithiazole rings are good ligands because the two nitrogen atoms in the bithiazole rings are able to chelate metal ions to form stable five-membered rings [2].
Schiff base type polymers, which have many special properties, such as thermal stability, liquid crystalline properties, conductivity, and chelating effects [3], [4], [5], have been drawing the attention of researchers for more than 50 years. A variety of Schiff base polymers had been synthesized and characterized [6]. Sun et al. [7], [8] synthesized bithiazole-containing polymers and found their metal complexes had typically ferromagnetic properties. These polymers and their derivatives were investigated as high-performance polymers for use in ferromagnetic materials, as well as new composite and photoelectronic materials. For this purpose, the material can be subjected to high temperature not only in the manufacturing, compounding and processing stage, but also in service or during repair [9], [10]. Since thermal stability is related to both the initial temperature and the rate of degradation of polymers, determination of kinetic parameters associated with the degradation processes is an interesting topic of research. Thermal analysis can also be used for the durability assessment and lifetime prediction of the product. Such a study is very important for the improvement of the service performance of the product, especially for critical applications in defense and aerospace, which would help build up user confidence in other potential applications.
The present paper reports on the synthesis, characterization and degradation kinetics of a novel polyester containing bithiazole rings. The degradation kinetics was followed using differential thermal analysis-thermogravimetry (DTA-TG). The non-isothermal kinetics of the decomposition process of the polyester was interpreted by the integral isoconversional method suggested by Kissinger–Akahira–Sunose (K–A–S) and iterative methods that give the best description of the studied decomposition process and allow the calculation of reliable values of the kinetic parameter.
Section snippets
Materials
4-Hydroxybenzaldehyde (PHBA, purity ≥ 99%) and 1,4-dibromo-2,3-butanedione (purity 98%) were purchased from Shanghai Chemical Reagent Company. 1,4-Benzenedicarbonyl dichloride (purity ≥ 99%) and dichloromethane (purity 99.8%) were obtained from J & K Technology Co., Ltd. Thiourea (purity 99%) was obtained from Sinopharm Chemical Reagent Co., Ltd. Acetone (purity 99.3%), ethanol and NaOH (purity 98%) were supplied by Shenzhen Meryer Chemical Technology Co., Ltd.
Synthesis of polyester
In a three-necked flask equipped with
FTIR analysis
The basic strategies employed for the synthesis of a novel polyester containing bithiazole is based on the Schiff base and Schotten–Baumann reactions. The structure of the Schiff base type BDDP was determined by IR spectroscopy. The spectra of DABT, 4-hydroxybenzaldehyde and BDDP can be seen in the FTIR spectra (Fig. 3). BDDP gives characteristic peaks in the range of 1400–1550 cm−1, which are due to the bithiazole rings. The stretching vibration of the new CN bond appears at about 1606 cm−1 for
Conclusions
A novel Schiff base type polyester based on bithiazole has been obtained from low-temperature interface polycondensation of 1,4-benzenedicarbonyl dichloride with 4,4′-(4,4′-bithiazole-2,2′-diylbis(imine-2,1-diyl)diphenol (BDDP). The polyester was characterized by FTIR spectroscopy, elemental analysis, X-ray diffraction and thermogravimetric analysis. A broad X-ray diffraction hump indicates that the polyester has an amorphous nature. The thermal degradation of the polyester in nitrogen has been
Acknowledgements
This work was financially supported by Education Office of Liaoning Province (No. 2008567) and State Key Laboratory of Robotics (RLO201016).
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