Browsing by Author "Hacaloglu, J."

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Open Access
Analysis of polymers using evolved-gas and direct-pyrolysis techniques
(Royal Society of Chemistry, 1994) Fares, M. M.; Yalcin, T.; Hacaloglu, J.; Gungor, A.; Süzer, Şefik
Thermal analysis of polystyrene, poly(p-methylstyrene) and poly(α-methylstyrene) has been carried out using evolved-gas analysis by infrared and mass spectrometry, and direct-pyrolysis analysis by mass spectrometric techniques. Evolved-gas analysis, both by infrared and mass spectrometry, reveals features due mainly to the corresponding monomers or stable, volatile, and low relative molecular mass degradation products. In direct-pyrolysis mass spectrometry, however, primary decomposition products and heavier fragments such as dimers and trimers can also be detected. The ion-temperature profiles of the corresponding monomer ions reveal information about the thermal stability of the polymers.
Open Access
Characterization of degradation products of polyethylene oxide by pyrolysis mass spectrometry
(Pergamon Press, 1994) Fares, M. M.; Hacaloglu, J.; Süzer, Şefik
The techniques of direct and indirect (evolved gas analysis) pyrolysis MS are used to characterize the thermal degradation products of polyethylene oxide. Using direct pyrolysis MS technique the main degradation process is determined to be due to CO and CC scissions yielding fragments characteristic of the polymer. Evolved gas analysis indicates formation of small molecular stable compounds such as C2H5OC2H5, CH3CHO, CO2, CO and C2H4. © 1994.
Open Access
A conducting composite of polythiophene: synthesis and characterization
(John Wiley & Sons Ltd., 1996) Vatansever, F.; Hacaloglu, J.; Toppare, L.
Conducting polymer composites of polythiophene, using a polyamide as the insulating matrix, were prepared via electrochemical methods. The characterization of the composite was done by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared and pyrolysis studies. The conductivities were measured by a four-probe technique. The cited methods revealed that the composites have properties different from those of simple mechanical mixtures of the two polymers.
Open Access
Conducting polymer composites of polythiophene with natural and synthetic rubbers
(Elsevier, 1996) Yigit, S.; Hacaloglu, J.; Akbulut, U.; Toppare, L.
Electrochemical synthesis of conducting polymer composites of polythiophene was achieved. Synthetic and natural rubbers were used as the insulating polymer matrices. FT-IR, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and mass spectrometry (MS) were utilized to characterize the composite blends. The conductivity measurements were done by using a standard four-probe technique. The above-mentioned methods show that the resultant composites have different properties compared to polythiophene due to interaction of the rubbers with electrochemical polymerization of thiophene, whereas the same argument is not valid for the polypyrrole synthesis via the same procedure.
Open Access
Cyclodextrin functionalized poly(methyl methacrylate) (PMMA) electrospun nanofibers for organic vapors waste treatment
(Elsevier BV, 2010) Uyar, Tamer; Havelund, R.; Nur, Y.; Balan, A.; Hacaloglu, J.; Toppare, L.; Besenbacher, F.; Kingshott, P.
Poly(methyl methacrylate) (PMMA) nanofibers containing the inclusion complex forming betacyclodextrin (_-CD) were successfully produced by means of electrospinning in order to develop functional nanofibrous webs for organic vapor waste treatment. Electrospinning of uniform PMMA nanofibers containing different loadings of _-CD (10%, 25% and 50% (w/w)) was achieved. The surface sensitive spectroscopic techniques; X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that some of the _-CD molecules are present on the surface of the PMMA nanofibers, which is essential for the trapping of organic vapors by inclusion complexation. Direct pyrolysis mass spectrometry (DP-MS) studies showed that PMMA nanowebs containing _-CD can entrap organic vapors such as aniline, styrene and toluene from the surroundings due to inclusion complexation with _-CD that is present on the fiber surface. Our study showed that electrospun nanowebs functionalized with cyclodextrinsmayhave the potential to be used as molecular filters and/or nanofilters for the treatment of organic vapor waste and air filtration purposes.
Open Access
Determination of electron affinity of phenyl radical by dissociative electron attachment technique
(John Wiley & Sons, 1993-03) Hacaloglu, J.; Gaines, A.; Süzer, Şefik
Open Access
Electrospinning of functional poly(methyl methacrylate) nanofibers containing cyclodextrin-menthol inclusion complexes
(Institute of Physics Publishing, 2009) Uyar, Tamer; Nur, Y.; Hacaloglu, J.; Besenbacher, F.
Electrospinning of nanofibers with cyclodextrin inclusion complexes (CD-ICs) is particularly attractive since distinct properties can be obtained by combining the nanofibers with specific functions of the CD-ICs. Here we report on the electrospinning of poly(methyl methacrylate) (PMMA) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). These CD-menthol-IC functionalized nanofibers were developed with the purpose of producing functional nanofibers that contain fragrances/flavors with high temperature stability, and menthol was used as a model fragrance/flavor material. The PMMA nanofibers were electrospun with CD-menthol-ICs using three type of CD: α-CD, β-CD, and γ-CD. Direct pyrolysis mass spectrometry (DP-MS) studies showed that the thermal evaporation of menthol occurred over a very high and a broad temperature range (100-355 °C) for PMMA/CDmenthol-IC nanowebs, demonstrating the complexation of menthol with the CD cavity and its high temperature stability. Furthermore, as the size of CD cavity increased in the order α-CD<β-CD<γ-CD, the thermal evolution of menthol shifted to higher temperatures, suggesting that the strength of interaction between menthol and the CD cavity is in the order γ-CD>β-CD>α-CD. © 2009 IOP Publishing Ltd.
Open Access
Electrospun polyethylene oxide (PEO) nanofibers containing cyclodextrin inclusion complex
(American Scientific Publishers, 2011) Uyar, Tamer; Hacaloglu, J.; Besenbacher, F.
In this study, we obtained functional electrospun nanofibers containing stable fragrance/flavor molecule facilitated by cyclodextrin inclusion complexation. Menthol was used as a model fragrance/flavor molecule and we have electrospun poly(ethylene oxide) (PEO) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-IC). We used two different solvent systems; water and water:ethanol and three types of CDs; α-CD, β-CD and γ-CD in order to find the optimal performance for the stabilization of menthol at high temperatures. We observed that the solvent system used for electrospinning process and the types of CDs (α-CD, β-CD and γ-CD) are very important to obtain CD-menthol-IC which ultimately determines the durability and temperature stability of menthol in the PEO nanofibrous web. We found out that it is better to use water rather than the water:ethanol solvent system for the inclusion complexation and additionally β-CD and γ-CD are most favorable choices since they are able to form complexation with menthol in the water solvent system. Despite the high volatility nature of menthol, our results demonstrated that the stability and temperature release of menthol was sustained to a very high and a broad temperature range (100 °C-250 °C) for PEO nanowebs containing CD-menthol-IC whereas the PEO nanofibers without CD and without CD-menthol complex could not preserve menthol even during storage. In brief, the results are very encouraging and open up for a variety of new exciting possibilities for the development of multi-functional electrospun nanofibers containing cyclodextrin inclusion complexes. Copyright © 2011 American Scientific Publishers All rights reserved.
Open Access
Functional electrospun polystyrene nanofibers incorporating α-, β-, and γ-cyclodextrins: Comparison of molecular filter performance
(2010) Uyar, Tamer; Havelund, R.; Hacaloglu, J.; Besenbacher, F.; Kingshott, P.
Electrospinning has been used to successfully create polystyrene (PS) nanofibers containing either of three different types of cyclodextrin (CD); α-CD, β-CD, and γ-CD. These three CDs are chosen because they have different sized cavities that potentially allow for selective inclusion complex (IC) formation with molecules of different size or differences in affinity of IC formation with one type of molecule. The CD containing electrospun PS nanofibers (PS/CD) were initially characterized by scanning electron microscopy (SEM) to determine the uniformity of the fibers and their fiber diameter distributions. X-ray photoelectron spectroscopy (XPS) was used to quantitatively determine the concentration of each CD on the different fiber surfaces. Static time-of-flight secondary ion mass spectrometry (static-ToF-SIMS) showed the presence of each type of CD on the PS nanofibers by the detection of both the CD sodium adduct molecular ions (M + Na+) and lower molecular weight oxygen containing fragment ions. The comparative efficiency of the PS/CD nanofibers/nanoweb for removing phenolphthalein, a model organic compound, from solution was determined by UV-vis spectrometry, and the kinetics of phenolphthalein capture was shown to follow the trend PS/α-CD > PS/β-CD > PS/γ-CD. Direct pyrolysis mass spectrometry (DP-MS) was also performed to ascertain the relative binding strengths of the phenolphthalein for the CD cavities, and the results showed the trend in the interaction strength was β-CD > γ-CD > α-CD. Our results demonstrate that nanofibers produced by electrospinning that incorporate cyclodextrins with different sized cavities can indeed filter organic molecules and can potentially be used for filtration, purification, and/or separation processes. © 2010 American Chemical Society.
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
Preparation and characterization of polystyrene-b-poly(2-vinylpyridine) coordinated to metal ion nanoparticles
(Elsevier, 2014-03) Lekesiz, T. O.; Kaleli, K.; Uyar, Tamer; Kayran, C.; Hacaloglu, J.
In this study, Co, Cr or Au3+ functional polystyrene-block- poly(2-vinylpyridine), PS-b-P2VP complexes were prepared and characterized. Coordination of metal atom or ion to nitrogen atom of pyridine rings was confirmed by FTIR analyses. The strength and efficiency of coordination of P2VP blocks to Co, Cr or Au3+ mainly depends on charge and stability of the complex formed that is mainly related to the energy of d orbitals. The results reveal that the thermal stability of the polymer composite formed increases with the increase in strength of the coordination. Changes in thermal decomposition mechanism and product distribution were recorded. Degradation of P2VP units coordinated to Cr, Co or Au3+ was started by loss of pyridine units leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures. © 2014 Elsevier B.V.
Open Access
Pyrolysis mass spectrometric analysis of styrene-butadiene block and random copolymers
(Elsevier, 1997-02) Hacaloglu, J.; Ersen, T.; Ertugrul, N.; Fares, M. M.; Süzer, Şefik
Direct pyrolysis mass spectrometric analysis of a styrene-butadiene-styrene block copolymer indicated that thermal decomposition of each block shows a resemblance to the related homopolymer, giving a possibility of differentiation of blocks. However, the random analog, the styrene butadiene rubber, degraded in a manner that is somewhat in between in nature of the thermal characteristics of both homopolymers. This technique shows promise to differentiate thermal behaviors of each sequence in block polymers if any exist. Indirect pyrolysis mass spectrometric analysis gave no clear evidence for differentiation of the nature and the composition of the copolymers. © 1997 Elsevier Science Ltd. All rights reserved.
Open Access
Pyrolysis mass spectrometric analysis of styrene-isoprene-styrene copolymers
(Elsevier, 1999-05) Hacaloglu, J.; Fares, M. M.; Süzer, Şefik
Thermal analysis of styrene±isoprene±styrene block copolymer, using the direct pyrolysis mass spectrometry (MS) technique, indicated that each block showed very similar thermal behavior with the corresponding homopolymer. The isoprene block was found to be thermally less stable, decomposing by random scissions followed by cyclization reactions. The more stable styrene block degraded by a radical depolymerization mechanism. With an indirect pyrolysis MS technique, it was found that production of benzene, toluene, 1-methyl cyclopentene and 1-methyl cyclohexene was more e ective when degradation was carried out in a closed reactor. # 1999 Elsevier Science Ltd. All rights reserved.
Open Access
A pyrolysis mass spectrometry study of polythiophene-natural rubber and polythiophene-synthetic rubber conducting polymer composites
(Elsevier, 1997) Yigit, S.; Hacaloglu, J.; Akbulut, U.; Toppare, L.
The thermal behaviors and degradation products of conducting polymer composites prepared by electrooxidation of thiophene using natural rubber or synthetic rubber as the insulating matrix were studied by direct and indirect mass spectrometry techniques. The pyrolysis mass data revealed that a chemical interaction formed between the components of the composites during polymerization. Thermal characteristics of rubbers totally disappeared in the composites indicating presence of some chain scissions leading to degradation of rubbers during electrooxidative polymerization. The multiscan cyclic voltammetry runs showed that polythiophene is also electroactive on the rubber coated metal electrodes, with a small shift in the redox peaks compared to the one on the bare electrode.
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