Journal of Analytical and Applied Pyrolysis 112 (2015) 37–47 Contents lists available at ScienceDirect Journal of Analytical and Applied Pyrolysis journal homepage: www.elsevier.com/locate/jaap Thermal and thermo-oxidative degradation of some heterocyclic aromatic polyethers containing phenylquinoxaline and/or 1,3,4-oxadiazole rings Gabriela Lisa a,∗ , Alina-Mirela Ipate b , Corneliu Hamciuc b , Nita Tudorachi b a Gheorghe Asachi Tehnical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Department of Chemical Engineering, 73 Prof.dr.doc D. Mangeron Street, 700050 Iasi, Romania b “Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, Iasi 700487, Romania article info Article history: Received 11 August 2014 Received in revised form 19 January 2015 Accepted 16 February 2015 Available online 19 February 2015 Keywords: Heterocyclic aromatic polyethers Thermal degradation Thermo-oxidative degradation TG/MS/FTIR abstract Poly(phenylquinoxaline ether ketone) Q-DFB and poly(phenylquinoxaline-1,3,4-oxadiazole ether) Ox- Q were synthesized by the conventional aromatic nucleophilic substitution polymerization technique of bis(hydroxyphenylquinoxaline) with 4,4 ′ -difluorodiphenyl ketone or with 2,5-bis(4-fluorophenyl)- 1,3,4-oxadiazole, respectively. Poly(1,3,4-oxadiazole ether) Ox-BisA was prepared by the same synthetic method from 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole, and 2,2-bis(4-hydroxyphenyl) propane. The polymers were characterized by Fourier transform infrared (FTIR) spectroscopy, solubility, the inherent viscosity and thermogravimetric analysis (TGA). The thermogravimetric analyzes were effectuated under air or helium atmosphere. Information on thermal decomposition onset in the two atmospheres was collected by using the TG/MS/FTIR technique (simultaneous mass spectrometry and Fourier transform infrared spectroscopy of off-gases from a thermogravimetric analyzer). The influence of phenylquinoxa- line and 1,3,4-oxadiazole rings on the thermodegradation behavior of the polymers was evidenced. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Polyphenylquinoxalines are a well-known class of high per- formance thermoplastics that exhibit good thermal oxidative and hydrolytic stability, moderately high glass transition tempera- tures, low dielectric constant and tough mechanical properties. They show excellent adhesive and film forming properties and could have potential applications in microlelectronics, structural resins for advanced aircraft in aerospace vehicles, gas separa- tion and ultafiltration membranes [1]. Due to their exceptional mechanical and thermal properties, and proton-conducting ability, polyphenylquinoxalines are also excellent candidates for investiga- tion as proton exchange membranes for high temperature fuel cells [2]. The presence of phenyl-substituted quinoxaline rings leads to polymers having higher thermostability, improved solubility and higher processability compared to the parent unsubstituted poly- mers [3]. However, polyphenylquinoxalines are soluble only in chlorinated solvents and m-cresol. The toxicity of these solvents may limit the use of the polymers in many applications. ∗ Corresponding author. Tel.: +40 232 271311; fax: +40 232 271311. E-mail addresses: gapreot@yahoo.com, gapreot@ch.tuiasi.ro (G. Lisa). Aromatic poly(1,3,4-oxadiazoles) have received considerable interest for the production of high performance materials due to their high thermal stability in oxidative atmosphere and good mechanical properties. 1,3,4-Oxadiazole ring can be considered similar to a p-phenylene structure, which is known to be highly thermoresistant. This heterocycle does not contain any hydrogen atoms, it does not have any possibilities of rearrangement, it has structural symmetry and is thermally unreactive [4]. Specific prop- erties determined by the electronic structure of 1,3,4-oxadiazole ring especially its electron-withdrawing character, led to an inten- sive research in order to use such polymers as advanced materials in microelectronics, optoelectronics and other [5]. On the others hand, aromatic polyoxadiazoles are rigid, rod-like molecules and are insoluble in organic solvents and do not have a glass transition temperature which makes their processing quite difficult. The introduction of ether linkages into the macromolecu- lar chains of aromatic poly(phenylquinoxalines) or poly(1,3,4- oxadiazoles) gave polymers with good processability. Thus, poly(aryl-ether-phenylquinoxalines) and poly(aryl-ether-1,3,4- oxadiazoles) show better solubility and melt processing charac- teristics than their counterparts containing only directly linked aromatic rings [6,7], while maintaining good thermal resistance properties. They can be applied in high performance applications that require in the same time good processability, high glass tran- http://dx.doi.org/10.1016/j.jaap.2015.02.025 0165-2370/© 2015 Elsevier B.V. All rights reserved.