The formation of conjugated structure and its transformation to pseudo-graphite structure during thermal treatment of polyacrylonitrile

Abstract

Three types of polyacrylonitrile (PAN) were considered in order to investigate the effect of molecular composition and configuration on the formation of conjugated structures during stabilization and the conversion of that to pseudo-graphite sheets after carbonization. The stabilization process was performed in an inert or oxidative atmosphere with a temperature ramp from 180°Cto 280°C. The thermal behavior was studied by differential scanning calorimetry, and the change of chemical groups and conjugated structures was detected by in situ measurement of infrared (Fourier transform infrared) and ultraviolet–visible spectroscopy, respectively. The carbonization process of the stabilized samples was performed using a thermogravimetric analyzer under nitrogen atmosphere in the temperature range of 150°C–1200°C, and Raman spectra were applied to study the pseudo-graphite sheets of the residuals. It is suggested that the introduction of comonomer or the improvement of the isotactic regularity of the polymer chain are helpful to promote the stabilization reactions and accelerate the formation of conjugated structures rather than the extent of conjugation during stabilization in nitrogen. Moreover, they are also beneficial to obtain higher degree of graphitization and larger size of the pseudo-graphite sheets with less structural defects after carbonization. While stabilization is performed in air, atactic PAN copolymer has the highest extent of stabilization among these three PAN samples, but they are extremely close. PAN samples with comonomer or higher isotacticity still show a little advantage in the formation speed of the conjugated structures. After carbonization, PAN with higher isotacticity has the highest carbon yield and graphitization degree and the largest size of pseudo-graphite sheets with least structural defects. In addition, the presence of oxygen during stabilization is contributory to increase the extent of stabilization and generate some bigger conjugated structures, which leads to obtain higher graphitization degree and larger size of pseudo-graphite sheets, but it also brings more structural defects.

Keywords

Polyacrylonitrile conjugated structures thermal treatment co-monomer stereoregularity pseudo-graphite sheets

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References

Dalton

Heatley

Budd

. Thermal stabilization of polyacrylonitrile fibres. Polymer 1999; 40: 5531–5543.

Rahaman

MSA

Ismail

Mustafa

. A review of heat treatment on polyacrylonitrile fiber. Polym Degrad Stab 2007; 92: 1421–1432.

Qin

Xiao

. Improving stabilization degree of stabilized fibers by pretreating polyacrylonitrile precursor in nitrogen. Mater Lett 2012; 76: 162–164.

Qin

Xiao

. A comparison of the effect of graphitization on microstructures and properties of polyacrylonitrile and mesophase pitch-based carbon fibers. Carbon 2012; 50: 4459–4469.

Hanna

Yehia

Ismail

. Preparation and characterization of carbon fibers from polyacrylonitrile precursors. J Appl Polym Sci 2012; 123: 2074–2083.

Liu

. Effects of chemical composition and post-spinning stretching process on the morphological, structural, and thermo-chemical properties of electrospun polyacrylonitrile copolymer precursor nanofibers. Polymer 2015; 61: 20–28.

Zhao

Wang

Bai

. Property changes of powdery polyacrylonitrile synthesized by aqueous suspension polymerization during heat-treatment process under air atmosphere. J Colloid Interface Sci 2009; 329: 48–53.

Rangarajan

Bhanu

Godshall

. Dynamic oscillatory shear properties of potential melt processable high acrylonitrile terpolymers. Polymer 2002; 43: 2699–2709.

Korobeinyk

Whitby

RLD

Mikhalovsky

. High temperature oxidative resistance of polyacrylonitrile-methylmethacrylate copolymer powder converting to a carbonized monolith. Eur Polym J 2012; 48: 97–104.

10.

Gupta

Paliwal

Bajaj

. Effect of the nature and mole fraction of acidic comonomer on the stabilization of polyacrylonitrile. J Appl Polym Sci 1996; 59: 1819–1826.

11.

Belyaeva

Krivtsov

Gaberling

. Oxidation process of polyacrylonitrile fibers. Fiber Chem 2013; 44: 268–272.

12.

Nguyen-Thai

Hong

. Controlled architectures of poly(acrylonitrile co-itaconic acid) for efficient structural transformation into carbon materials. Carbon 2014; 69: 571–581.

13.

Wang

Pang

. Stereoregularity of polyacrylonitrile studied by high-resolution ¹³C-NMR spectroscopy. Chin J Magn Reson 2008; 25: 176–183.

14.

Zou

Wang

Pang

. Radiation-induced inclusion polymerization of acrylonitrile in urea canals: toward synthesis of completely isotactic polyacrylonitrile with controlled molecular weight. Macromolecules 2013; 46: 1765–1771.

15.

Minagawa

Yamada

Yamaguchi

. γ-Ray irradiation canal polymerization conditions ensuring highly stereoregular (>80%) poly(acrylonitrile). Macromolecules 1992; 25: 503–510.

16.

Tin

Geiderkh

Davydov

. Influence of the stereoregularity of macromolecules on the process of formation and growth of the structure of effective conjugation in polyacrylonitrile. Russ Chem Bull 1970; 19: 1911–1916.

17.

Bashir

Manns

Service

. Investigation of base induced cyclization and methine proton abstraction in polyacrylonitrile solutions. Polymer 1991; 32: 1826–1833.

18.

Coleman

Givy

Painter

. Studies of the degradation of acrylonitrile/acrylamide copolymers as a function of composition and temperature. Carbon 1983; 21: 255–267.

19.

Kubasova

Din

Heiderich

. Effect of the stereoregularity of polyacrylonitrile macromolecules on the formation of conjugated bond structure. Polym Sci USSR 1971; 13: 184–190.

20.

Park

Lee

Joh

. Effect of functional groups of carbon nanotubes on the cyclization mechanism of polyacrylonitrile (PAN). Polymer 2012; 53: 2168–2174.

21.

Ouyang

Cheng

Wang

. DSC study of stabilization reactions in poly(acrylonitrile-co-itaconic acid) with peak resolving method. J Therm Anal Calorim 2008; 94: 85–88.

22.

Xiao

Tong

. Thermal behavior and kinetics during the stabilization of polyacrylonitrile precursor in inert gas. J Appl Polym Sci 2011; 122: 480–488.

23.

Gupta

Paliwal

Bajaj

. Effect of an acidic comonomer on the thermooxidative stabilization of polyacrylonitrile. J Appl Polym Sci 1995; 58: 1161–1174.

24.

Ouyang

Cheng

Wang

. Mechanism and kinetics of the stabilization reactions of itaconic acid-modified polyacrylonitrile. Polym Degrad Stab 2008; 93: 1415–1421.

25.

Arbab

Mirbaha

Zeinolebadi

. Indicators for evaluation of progress in thermal stabilization reactions of polyacrylonitrile fibers. J Appl Polym Sci 2014; 131: 40343.

26.

Kim

Shin

Kim

. Thermal characterization of chitosan and polyacrylonitrile semi-interpenetrating polymer networks. High Perform Polym 2002; 14: 309–316.

27.

Minagawa

Miyano

Takahashi

. Infrared characteristic absorption bands of highly isotactic poly(acrylonitrile). Macromolecules 1988; 21: 2387–2391.

28.

Guo

Chen

. Preparation and characterization of polyacrylonitrile doped PVDF/heteropoly acid composite membranes. High Perform Polym 2012; 24: 282–288.

29.

Fochler

Mooney

Ball

. Infrared and NMR spectroscopic studies of the thermal degradation of polyacrylonitrile. Spectrochim Acta Part A 1985; 41: 271–278.

30.

Cipriani

Zanetti

Bracco

. Crosslinking and carbonization process in PAN films and nanofibers. Polym Degrad Stab 2016; 123: 178–188.

31.

Wang

Xiao

Cao

. Evolution of aggregation structure of polyacrylonitrile fibers in the cyclization reaction. J Appl Polym Sci 2012; 124: 3413–3418.

32.

Tian

Han

Zhang

. Influence of residence time on the structure of polyacrylonitrile in ionic liquids during melt spinning process. Mater Lett 2013; 92: 119–121.

33.

Wang

. Structural identification of polyacrylonitrile during thermal treatment by selective ¹³C labeling and solid-state ¹³C NMR spectroscopy. Macromolecules 2014; 47: 3901–3908.

34.

Liu

Chen

Hong

. Stabilization of atactic-polyacrylonitrile under nitrogen and air as studied by solid-state NMR. Macromolecules 2015; 48: 5300–5309.

35.

Zhao

Jiang

. The effect of γ-ray irradiation on the microstructure and thermal properties of polyacrylonitrile fibers. RSC Adv 2015; 5: 23508–23518.

36.

Usami

Ohtani

Tsuge

. Structural study of polyacrylonitrile fibers during oxidative thermal degradation by pyrolysis-gas chromatography, solid-state ¹³C nuclear magnetic resonance, and Fourier transform infrared spectroscopy. Macromolecules 1990; 23: 2460–2465.

37.

Daranyi

Sarusi

Sapi

. Characterization of carbon thin films prepared by the thermal decomposition of spin coated polyacrylonitrile layers containing metal acetates. Thin Solid Films 2011; 520: 57–63.

38.

Jawhari

Roid

Casado

. Raman spectroscopic characterization of some commercially available carbon black materials. Carbon 1995; 33: 1561–1565.

39.

Kim

Park

Cho

. Raman spectroscopic evaluation of polyacrylonitrile-based carbon nanofibers prepared by electrospinning. J Raman Spectrosc 2004; 35: 928–933.

40.

Bai

Cai

Qiu

. Effects of graphene reduction degree on thermal oxidative stability of reduced graphene oxide/silicone rubber nanocomposites. High Perform Polym 2015; 27: 997–1006.