Browsing by Author "Ishida, H."

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Open Access
Investigation of polymerization of benzoxazines and thermal degradation characteristics of polybenzoxazines via direct pyrolysis mass spectrometry
(Wiley, 2012-10) Bagherifarm, S. B.; Uyar, Tamer; Ishida, H.; Hacaloglu, J.
Polymerization of benzoxazines and thermal degradation mechanisms of polybenzoxazines were investigated using the direct pyrolysis mass spectrometry (DP-MS) technique. The benzoxazine structures were based on phenol and aniline and on bisphenol-A and methylamine or aniline. Polymerizations of the benzoxazines were carried out by curing them at elevated temperatures without addition of initiator or catalyst. DP-MS data showed the presence of chains generated by opposing polymerization reaction pathways indicating quite complex structures for the polybenzoxazines under investigation. Thermal decomposition of polybenzoxazines was started by the cleavage of methylamine or aniline linkages. It was determined that polybenzoxazines based on phenol were more stable than the corresponding bisphenol-A-based polybenzoxazines, while those based on methylamine were more stable than the corresponding polybenzoxazines incorporating aniline. Thus, it can be concluded that the presence of bulky groups decreased the extent of crosslinking which in return decreased the thermal stability. © 2012 Society of Chemical Industry.
Open Access
Molecular catalysts for artificial photosynthesis: general discussion
(Royal Society of Chemistry, 2017) Wang, M.; Artero, V.; Hammarström, L.; Martinez, J.; Karlsson, J.; Gust, D.; Summers, P.; Machan, C.; Brueggeller, P.; Windle, C. D.; Kageshima, Y.; Cogdell, R.; Tolod, K. R.; Kibler, A.; Apaydin, D. H.; Fujita, E.; Ehrmaier, J.; Shima, S.; Gibson, E.; Karadas, F.; Harriman, A.; Inoue, H.; Kudo, A.; Takayama, T.; Wasielewski, M.; Cassiola, F.; Yagi, M.; Ishida, H.; Franco, F.; Kang, S. O.; Nocera, D.; Li C.; Fonzo, F. D.; Park, H.; Sun, L.; Setoyama, T.; Kang, Y. S.; Ishitani, O.; Shen, J. R.; Son, H. J.; Masaoka, S.
Open Access
Synthesis, characterization and thermal properties of Alkyl-functional naphthoxazines
(Wiley, 2013-02-15) Uyar, Tamer; Hacaloglu, J.; Ishida, H.
A series of alkyl-functional naphthoxazine resins having various alkyl chain lengths from C1 to C18 are synthesized with a high yield and high purity by the reactions of 1,5-dihydroxynaphthalene, formaldehyde, and aliphatic amines. The proposed chemical structures of the naphthoxazines are confirmed by high-resolution mass spectrometry, H-1 nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and pyrolysis mass spectrometry studies. The alkyl-functional naphthoxazines have shown low polymerization temperature characteristics where polymerization of these monomers is achieved in the range of 150-170 degrees C yielding cross-linked polynaphthoxazines. The low-temperature polymerization characteristics and the associated thermal degradation behaviors are studied. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 3114-3123, 2013
Open Access
Thermal degradation mechanisms of polybenzoxazines
(Elsevier, 2011) Hacaloǧlu, J.; Uyar, T.; Ishida, H.
This chapter explains the thermal degradation processes of various Polybenzoxazines and the degradation mechanisms. The structural effects of phenols and amines on the thermal degradation of polybenzoxazines are investigated systematically. The thermal decomposition studies of polybenzoxazines are sometimes difficult because a large number of degradation products are released during the pyrolysis of polybenzoxazines; therefore, model dimmers and oligomers of polybenzoxazines are also examined to have a clear understanding of the thermal degradation mechanisms of polybenzoxazines. Here, the findings related to the thermal degradation processes of polybenzoxazines and the proposed degradation mechanisms for polybenzoxazines are summarized. This chapter explores that among the several techniques used to investigate the thermal characteristics of polymers, thermogravimetric analyzer (TGA), TGA interfaced with Fourier transform infrared spectroscopy (FTIR) or gas chromatography-mass spectrometry (GC-MS), and pyrolysis techniques coupled with FTIR, GC-MS, and MS provide information on thermal degradation products. FTIR combined with TGA or a pyrolysis technique provides information about the type and functionality of the degradation products as a function of time and/or temperature. The use of GC-MS instead of FTIR allows the separation and identification of degradation products. However, condensation of high mass pyrolysates and reactions between the decomposition products during the transport of degradation products from TGA or pyrolyzer system to FTIR or GC-MS are highly probable.