Oxidative Degradation Of Poly Research Articles

Effect of Antioxidant 1010 on Oxidative Degradation of Poly（lactic acid） for 3D Printing

Effect of Antioxidant 1010 on Oxidative Degradation of Poly（lactic acid） for 3D Printing

Mass spectrometry investigation into the oxidative degradation of poly(ethylene glycol)

Poly(ethylene glycol) (PEG) is an inexpensive, commercially available polymer that has many biomedical and material applications. Due to its water-solubility and biocompatibility, it has been used in drug conjugation, as a humectant, as an anti-foaming agent in food, and as a stabilizer for preservation of antique wooden objects. Despite the robust applications of PEG, the products of oxidative degradation are not fully understood. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the end groups of PEG oxidative degradation products can be proposed. Confirmation of the proposed end groups can be corroborated via selective functionalization reactions as well as electrospray ionization (ESI) tandem mass spectrometry (MS2). Furthermore, the oxidative degradation mechanism of PEG is described here by examining the degradative products using these aforementioned techniques. These findings suggest consistent oxidative behavior for both narrowly dispersed and monodisperse PEG. However, examination of monodisperse PEG allowed for the elucidation of certain degradation behavior due to the presence of a single starting peak, rather than a distribution of peaks, as found in narrowly dispersed PEG. These results demonstrate that MALDI-TOF MS, ESI MS2, and selective functionalization reactions can be applied to the elucidation of polymer end groups and aid in identifying degradation mechanisms.

The effect of electric field on the oxidative degradation of polybenzimidazole membranes using electro-Fenton test

The degradation of membranes in proton exchange fuel cells by chemical oxidation is one of the main factors limiting their lifetime. The effect of electric field on the oxidative degradation of poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI) was investigated using electro-Fenton tests. The degraded PBI was characterized by measuring the sample's intrinsic viscosity (ηint) and weight loss and using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), and X-ray photoelectron spectroscopy (XPS). When the intensity of the electric field was increased from 0 V/m to 5000 V/m, the membrane's weight decreased, while the ηint of PBI decreased rapidly. Meanwhile, a larger number of larger pores formed on the PBI membranes, according to SEM images. The thermal stabilities of the degraded PBI membranes decreased significantly when the intensity of the electric field increased. FTIR, 1H NMR, and XPS spectra revealed that an electric field accelerated the formation of amide and amino groups after the breakdown of benzimidazole rings in PBI. The amino groups were stabilized by protonation in the acidic Fenton reagent. A possible mechanism for the increased oxidative degradation of PBI in an electric field was proposed.

Oxidative degradation of poly(3-hydroxybutyrate). A new method of synthesis for the malic acid copolymers

Herein was presented by the first time the green way to obtain poly(3-hydroxybutyrate-co-3-malic acid) from natural origin poly(3-hydroxybutyrate).

The Competition between Processes of Oxidative Polymerisation of 2-Methoxyaniline and Oxidative Degradation of Poly-(2-Methoxyaniline)

The kinetics of oxidative polymerisation of 2-methoxyaniline was investigated, and the activation energies of stages of single-electron transfer and complex formation were determined. The parallel occurrence of oxidative degradation of poly-(2-methoxyaniline) under conditions of oxidative polymerisation of 2-methoxyaniline was established.

Comparative analysis of in vitro oxidative degradation of poly(carbonate urethanes) for biostability screening

The resistance to oxidation and environmental stress cracking of poly(carbonate urethanes) (PCUs) has generated significant interest as potential replacements of poly(ether urethanes) in medical devices. Several in vitro models have been developed to screen segmented polyurethanes for oxidative stability. High concentrations of reactive oxygen intermediates produced by combining hydrogen peroxide and dissolved cobalt ions has frequently been used to predict long-term oxidative degradation with short-term testing. Alternatively, a 3% H₂O₂ concentration without metal ions is suggested within the ISO 10993-13 standard to simulate physiological degradation rates. A comparative analysis which evaluates the predictive capabilities of each test method has yet to be completed. To this end, we have utilized both systems to test three commercially available PCUs with low and high soft segment content: Bionate PCU and Bionate II PCUs, two materials with different soft segment chemistries, and CarboSil TSPCU, a thermoplastic silicone PCU. Bulk properties of all PCUs were retained with minor changes in molecular weight and tensile properties indicating surface oxidative degradation in the accelerated system after 36 days. Soft segment loss and surface damage were comparable to previous in vivo data. The 3% H₂O₂ method exhibited virtually no changes on the surface or in bulk properties after 12 months of treatment despite previous in vivo results. These results indicate the accelerated test method more effectively characterized the oxidative degradation profiles than the 3% H₂O₂ treatment system. The lack of bulk degradation in the 12-month study also supports the hydrolytic stability of these PCUs.

Enzymatic and oxidative degradation of poly(polyol sebacate)

Poly(glycerol sebacate) (PGS) and poly(xylitol sebacate) (PXS) are biodegradable elastomers with tremendous potential in soft tissue engineering. This study was aimed at exploring the enzymatic degradation mechanisms of these polyesters, using biochemical conditions similar to those occurring in vivo. To this end, PGS and PXS (crosslinked at 130 for 2 or 7 (PGS)/12 days (PXS)) were incubated in vitro under physiological conditions in tissue culture media supplemented with either a biodegrading enzyme (esterase), an oxidant species (FeSO4/H2O2 with 0.11 molar ratio of Fe(2+/)H2O2), an oxidant generating enzyme (xanthine oxidase and xanthine) or combinations of these (FeSO4/H2O2 and esterase, or (v) xanthine oxidase/xanthine and esterase), based on their independent effects on polymer degradation. Testing was performed over 35 days of continuous incubation, during which mechanical properties, mass loss, biomaterial thickness and pH value of the culture medium were determined. Degradation kinetics of both PGS and PXS samples were primarily determined by the degree of crosslink density. Esterase and FeSO4/H2O2 accelerated the degradation of both polymers, by promoting hydrolysis and free-radical degradation, although this action was not affected by the presence of xanthine oxidase and xanthine. Degradation of PGS and PXS is primarily mediated by the action of esterase, with free-radical oxidation playing a secondary role, suggesting that both could synergistically affect the biodegradability of biomaterial implants, under more complex biological conditions.

Mechanistic studies on the photodegradation of 2,5-dialkyloxyl-substituted para-phenylenevinylene oligomers by singlet oxygen

Time-dependent UV/visible absorption changes are observed on photolysis of aerated solutions of monodisperse, vinyl end-capped 2,5-diheptyloxyl substituted PV-oligomers (OPV, n = 1, 2, 3). In all cases, photolysis occurs in at least two distinct stages. Evidence for the intermediacy of singlet oxygen comes from pulse radiolysis and time-resolved luminescence studies, which confirm formation of the OPV triplet state and its quenching by molecular oxygen to produce singlet oxygen. The subsequent reaction with oligomers is observed directly by time-resolved phosphorescence and indirectly through product identification. The results strongly suggest that the reaction between singlet oxygen and OPV proceeds via cycloaddition, leading to bond scission and aldehyde group formation. The reactivity of vinylene linkages is greater than of vinyl end groups. Consequently, the photostability decreases as the chain length is extended. Implications on the oxidative degradation of poly(p-phenylenevinylene)s in optoelectronic devices, and of competing singlet oxygen and superoxide radical anion degradation pathways, are discussed.

Oxidative and photooxidative degradation of poly(acrylic acid)

The oxidative degradation of poly(acrylic acid) (PAA), a water soluble polymer, was studied at various temperatures with different concentrations of persulfates, potassium persulfate (KPS), ammonium persulfate (APS) and sodium persulfate (SPS). The photodegradation of PAA was also examined with APS as oxidizer. The degraded samples were analyzed for the time evolution of molecular weight distribution by gel permeation chromatography. A theoretical model based on the continuous distribution kinetics was developed that accounted for the polymer degradation and the dissociation of persulfate. The rate coefficients for the oxidative and photooxidative degradation of PAA were determined from the parametric fit of the model with experimental data. The rate of degradation increased with increasing amount of persulfate in both oxidative and photooxidative degradation. The rate of degradation also increased with increasing temperature in the case of oxidative degradation.

Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)

AbstractThe kinetics of the thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide) were determined with potassium persulfate as the oxidizing agent. Gel permeation chromatography was used to determine the variation of the molecular weight with time. The degradation was studied as a function of the temperature and persulfate concentration, and it was found that the degradation rate increased with the temperature and concentration of persulfate. Continuous distribution kinetics were used to determine the rate coefficients for the degradation process, and the activation energies were obtained. The results indicated that the microwave‐assisted process had a lower activation energy of 10.3 kcal/mol, whereas that of the thermal degradation was 25.2 kcal/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2090–2096, 2005

Oxidative degradation of poly (vinyl acetate) and poly ( ε-caprolactone) and their mixtures in solution

The oxidative degradation of the poly ( ε-caprolactone) (PCL), poly (vinyl acetate) (PVAC) and their mixtures in dichlorobenzene has been investigated at various temperatures (70–130°C) in the presence of benzoyl peroxide. The interaction between the polymers is quantified by monitoring the molecular weights of individual polymers using gel-permeation chromatography. The various physical mixtures employed in the present investigation are 20 80 , 50 50 and 80 20 wt%/wt% PCL/PVAC. Experimental data indicated that the degradation is random without cross-linking and repolymerization. An optimum in degradation temperature (corresponding to maximum degradation rate) of 105°C was observed for the entire range of polymer compositions (0–100% PCL) investigated. This optimum temperature of degradation is characteristic mostly of the initiator and only to a small extent of the degrading polymer system. The experimental results of the mixtures indicated that the degradation rates of PVAC are significantly enhanced, while the degradation rates of PCL are decreased in the physical mixture. This can be attributed to the proton-accepting and proton-donating nature of PCL and PVAC, respectively. A radical mechanism for the oxidative degradation of pure polymers and their mixtures has been proposed and a model based on continuous distribution kinetics was developed considering the interaction of the polymers through hydrogen abstraction and the parameters were evaluated numerically. The activation energies for the peroxide attack for the PCL and PVAC are 10.5 and 10.6 kcal mol −1 , respectively. The activation energies for the random chain scission of PCL and PVAC are 10.6 and 14.5 kcal mol −1 , respectively.

Continuous distribution kinetics for oxidative degradation of PMMA in solution

The oxidative degradation of poly(methyl methacrylate) (PMMA) was investigated in chlorobenzene at 50–100°C for various peroxide and polymer concentrations. Unlike thermal degradation, the chain scission of PMMA occurs randomly across the polymer backbone. The samples were analyzed by gel permeation chromatography (GPC) to obtain the time evolution of molecular weight distributions (MWDs). A continuous distribution model for polymer degradation and simultaneous peroxide deactivation was developed assuming that the rate coefficients depend linearly on MW. This model was used to determine the rate coefficients for the oxidative degradation of PMMA. The activation energy, determined from the temperature dependence of the rate coefficients, was 48.2 kcal/mol.

Thermo and photo-oxidation of polyisobutylene—II. Influence of the temperature

The influence of the temperature on the mechanism of photo-oxidation of poly(isobutylene) was studied for temperatures of the samples ranging from 30 to 90°C. The oxidation resulting from exposures to UV light at these various temperatures was compared to that obtained by thermo-oxidations carried out in the range 30–120°C. The oxidation was followed by FTIR analysis coupled with chemical derivatizations. The relative variations in the intensities of bands at 890, 1702, 1730 and 1832 cm −1 permitted a comparison of the behaviour of the polymer at the various temperatures. The results presented in this article show that the oxidative degradation of poly(isobutylene) can be explained in terms of an induced oxidation, even for the highest temperatures where the effect was investigated here.

Stabilising effect of derivatives of jatropha seed oil on the thermal degradation of poly(vinyl chloride)

Nonoxidative and oxidative degradation studies on poly(vinyl chloride) were carried out at various temperatures in the presence of Jatropha seed oil, epoxidised Jatropha seed oil and metal soaps of the oils. The rate of dehydrochlorination at 1% conversion, the time required for degradation to attain 1% dehydrochlorination and changes in intrinsic viscosity, UV absorption spectra and levels of unsaturation in the degraded polymer samples have been used to assess the effects of the derivatives of Jatropha seed oil on the susceptibility of the polymer to degradation. Although the values of the rate of dehydrochlorination at 1% conversion were about the same order of magnitude (10 −2% min −1), it was found that in the presence of the derivatives of Jatropha seed oil, particularly the metal soaps of epoxidised Jatropha seed oil, the values of the rate of dehydrochlorination were relatively lower and the time required for degradation to attain 1% conversion considerably higher than the values obtained in the absence of the additives. The data from solution viscosity measurements and from the estimates of the number of double bonds formed in the degraded polymer samples indicate that the metal soaps of Jatropha seed oil and of its epoxides exert a stabilising effect on the nonoxidative and oxidative degradation of poly(vinyl chloride).

Oxidative Degradation of Poly(3-octylthiophene)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxidative Degradation of Poly(3-octylthiophene)Nils Ljungqvist and Thomas HjertbergCite this: Macromolecules 1995, 28, 18, 5993–5999Publication Date (Print):August 1, 1995Publication History Published online1 May 2002Published inissue 1 August 1995https://doi.org/10.1021/ma00122a002RIGHTS & PERMISSIONSArticle Views385Altmetric-Citations38LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (749 KB) Get e-Alerts Get e-Alerts

Durability of radiation‐sterilized polymers, XIII. The effects of nucleating agent on the oxidative degradation of poly(propylene‐co‐ethylene)

AbstractThe radiation stability of the random and block poly(propylene‐co‐ethylene) (CP, copolymer with 6% ethylene units) with and without nucleating agent (NA) was compared in relation to radiation sterilization of medical supplies. In both cases, it was found that the radiation stability of CP in the presence of NA was lower than that of CP without NA.Addition of NA to CP did not improve the transparency but the crystallization occurred at higher temperature. Thus, adding NA to CP has the advantage of shorter moulding time in the production of medical supplies.The radiation instability of the CP with NA was due to a different crystal structure, because the spherulite shape differs from that of CP without NA. Furthermore, by the chemiluminescence analysis, a higher oxidative degradation was observed in the sample with NA.

A comparison of pyrolytical and oxidative degradation of poly(methyl methacrylate) and methyl methacrylate-styrene copolymer using the capillary GC and GC-MS methods

The thermal degradation of poly(methyl methacrylate) (PMMA) and of a methyl methacrylate copolymer with styrene (MMA-ST) were studied in an inert atmosphere and in the air, under conditions simulating a fire. Tubular furnace and high-frequency pyrolyzers were compared. The combustion products were analyzed using the capillary GC and GC-MS methods.

Application of evolved gas analysis to the study of poly(vinyl butyral) thermal stability

The study of polymer stability can often be aided by the determination of the chemical mechanisms involved in a specific mode of degradation. The technique of evolved gas analysis (EGA) has been combined with kinetic FTIR to identify the reaction products of the thermal and oxidative degradation of poly(vinyl butyral). The data suggests a mechanism involving dehydration of vinyl alcohol functionalities followed by oxidative attack.

Effects of weak linkages on the thermal and oxidative degradation of poly(methyl methacrylates)

Effects of weak linkages on the thermal and oxidative degradation of poly(methyl methacrylates)

Thermal and oxidative degradation of poly(methyl methacrylate): weight loss

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal and oxidative degradation of poly(methyl methacrylate): weight lossT. Hirata, Takashi Kashiwagi, and J. E. BrownCite this: Macromolecules 1985, 18, 7, 1410–1418Publication Date (Print):July 1, 1985Publication History Published online1 May 2002Published inissue 1 July 1985https://doi.org/10.1021/ma00149a010RIGHTS & PERMISSIONSArticle Views1751Altmetric-Citations212LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts