Investigation of polymerization of benzoxazines and thermal degradation characteristics of polybenzoxazines via direct prolysis mass spectrometry

Cataloged from PDF version of article.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

Pyrolysis Mass Spectrometric Analysis of styrene butadiene block and random copolymers

Cataloged from PDF version of article.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

Electrospun polyethylene oxide (PEO) nanofibers containing cyclodextrin inclusion complex

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

Characterization of degradation products of polyethylene oxide by pyrolysis mass spectrometry

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

A pyrolysis mass spectrometry study of polythiophene - Natural rubber and polythiophene - Synthetic rubber conducting polymer composites

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

Conducting polymer composites of polythiophene with natural and synthetic rubbers

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

Thermal decomposition of polystyrene-b-poly(2-vinylpyridine) coordinated to co nanoparticles

Direct pyrolysis mass spectrometry analyses of polystyrene-block-poly(2-vinylpyridne), PS-b-P2VP, indicated that the thermal degradation of each component occurred independently through the decomposition pathways proposed for the corresponding homopolymers; depolymerization for PS and depolymerization and loss of protonated oligomers for P2VP by a more complex degradation mechanism. On the other hand, upon coordination to cobalt nanoparticles, thermal decomposition of the P2VP blocks was initiated by loss of pyridine units, leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures. © 2009 Elsevier Ltd. All rights reserved

Preparation and characterization of polystyrene-b-poly(2-vinylpyridine) coordinated to metal ion nanoparticles

Cataloged from PDF version of article.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