Photo-Oxidation of Polymers without Light: Oxidation of Polybutadiene and an ABS Polyblend with Singlet Oxygen

1971 ◽  
Vol 44 (3) ◽  
pp. 642-652 ◽  
Author(s):  
M. L. Kaplan ◽  
P. G. Kelleher
Keyword(s):  
Singlet Oxygen ◽  
Structural Changes ◽  
Oxidative Degradation ◽  
Homogeneous Solution ◽  
Chain Scission ◽  
Standard Samples ◽  
Electronically Excited ◽  
Cis And Trans ◽  
Excited Oxygen

Abstract In recent years much evidence has been accumulated to implicate electronically excited oxygen ((1Δg)) molecules as the agent responsible in photo-sensitized oxidations for the formation of allylic hydroperoxides from olefins and of endoperoxides from 1 ,3-dienes. Little regarding the mechanistic aspects of the photo-oxidative degradation of polybutadiene is known, however. To determine if electronically excited oxygen ((1Δg)) molecules can oxidize PBD, the ABS polyblend and standard samples of PBD's containing high trans, high cis, and high vinyl content were treated in homogeneous solution at low temperature with chemically produced singlet oxygen in situ. The source of the singlet oxygen was the triphenylphosphite-ozone adduct. Studies by spectroscopy, elemental analysis, viscosity determinations, and gel measurements showed only the cis- and the trans-PBD were susceptible to oxidation; no chain scission was involved in the attack of cis- and trans-PBD by singlet oxygen; the oxidation of the cis-PBD involved the initial formation of hydroperoxides which on thermal decomposition yielded gel. The trans-PBD was found to oxidize but apparently by a mechanism different from that of cis-PBD. Initial singlet oxygen attack of ABS proceeds by oxidation of the PBD portion of the polyblend. It was also observed that when only a small amount of the double bonds in the cis-PBD polymer had been oxidized to hydroperoxides, subsequent thermal treatment of this sample resulted in gross structural changes in the whole polymer.

Polydiene Oxidations with Singlet Oxygen

1972 ◽  
Vol 45 (2) ◽  
pp. 423-436 ◽  
Author(s):  
M. L. Kaplan ◽  
P. G. Kelleher
Keyword(s):  
Singlet Oxygen ◽  
Gas Phase ◽  
Molecular Oxygen ◽  
Ground State ◽  
Homogeneous Solution ◽  
Surface Oxidation ◽  
Electrodeless Discharge ◽  
Photosensitized Oxidation

Abstract Excited molecular oxygen in its singlet delta (1Δg) state can be made chemically in homogeneous solution and in the gas-phase by the electrodeless discharge of ground state oxygen. Both techniques have been used to perform oxidations of polydiene systems. Solutions of high cis, trans, and vinyl polybutadienes have been treated with singlet oxygen produced in situ. Only the high cis and high trans were oxidized, apparently by different mechanisms. Squalene, a model for polyisoprene, has been oxidized in solution and the initially formed hydroperoxides reduced and analyzed and found identical to the product from a photosensitized oxidation. Cis-polybutadiene films were treated with gas-phase singlet oxygen and the extent of surface oxidation was monitored spectroscopically and chemically.

A Phenomenological Analysis of Exergy Destruction During Hydrogen Combustion With Electronically Excited Oxygen

2013 ◽  
Author(s):  
DeVon A. Washington ◽  
Howard N. Shapiro
Keyword(s):  
Singlet Oxygen ◽  
Flow Reactor ◽  
Hydrogen Oxidation ◽  
Combustion Process ◽  
Hydrogen Combustion ◽  
Exergy Destruction ◽  
Exergetic Efficiency ◽  
Optimal Range ◽  
Electronically Excited ◽  
Excited Oxygen

This study investigates the effects of introducing electronically excited oxygen on trends in exergy destruction during hydrogen combustion. Electronically excited oxygen enhances many properties of combustion. By understanding how it alters the chemical kinetics, and hence the destruction of exergy, it may be possible to improve the overall exergetic efficiency of combustion thereby reducing fuel use to achieve desired energy conversion. A numerical model was developed of an adiabatic plug flow reactor using CHEMKIN-PRO; in conjunction with a hydrogen oxidation mechanism that includes explicit reaction pathways for various electronically excited species. Exergy destruction was calculated for cases where singlet oxygen composed 0%–100% of the oxidizer while maintaining a stoichiometric oxidizer-fuel ratio; all other inlet conditions were held fixed. Results show that an optimal range of exergetic combustion efficiency exists between 0%–20%, with the maximum occurring at approximately 10%. A detailed assessment of the total exergy destruction reveals that, for the optimal range of exergetic combustion efficiencies, as much as 60% of the total exergy destruction occurs prior to ignition. For inlet percentages of singlet oxygen greater than 20%, the majority of the total exergy destruction occurs after ignition. This paper examines the phenomenological events taking place in the reaction mechanism that give rise to the destruction of exergy during combustion. Understanding these mechanisms and the effects of introducing excited oxygen into the combustion process, sheds light on how we might use excited oxygen to increase the exergetic efficiency of combustion.

Roughened gold electrode for in situ SERS analysis of structural changes accompanying the doping process of polyaniline in acidic aqueous media

2021 ◽  
Vol 882 ◽  
pp. 115034
Author(s):  
A. El Guerraf ◽  
M. Bouabdallaoui ◽  
Z. Aouzal ◽  
S. Ben Jadi ◽  
N.K. Bakirhan ◽  
...  
Keyword(s):  
Gold Electrode ◽  
Structural Changes ◽  
Aqueous Media

scholarly journals High temperature structural study of decagonal Al-Cu-Rh quasicrystal.

2014 ◽  
Vol 70 (a1) ◽  
pp. C94-C94
Author(s):  
Pawel Kuczera ◽  
Walter Steurer
Keyword(s):  
Structural Changes ◽  
Configurational Entropy ◽  
Lattice Vibrations ◽  
X Ray Diffraction ◽  
Stabilization Mechanism ◽  
X Ray ◽  
Comparative Structure ◽  
The Stability

The structure of d(ecagonal)-Al-Cu-Rh has been studied as a function of temperature by in-situ single-crystal X-ray diffraction in order to contribute to the discussion on energy or entropy stabilization of quasicrystals (QC) [1]. The experiments were performed at 293 K, 1223 K, 1153 K, 1083 K, and 1013 K. A common subset of 1460 unique reflections was used for the comparative structure refinements at each temperature. The results obtained for the HT structure refinements of d-Al-Cu-Rh QC seem to contradict a pure phasonic-entropy-based stabilization mechanism [2] for this QC. The trends observed for the ln func(I(T1 )/I(T2 )) vs.|k⊥ |^2 plots indicate that the best on-average quasiperiodic order exists between 1083 K and 1153 K, however, what that actually means is unclear. It could indicate towards a small phasonic contribution to entropy, but such contribution is not seen in the structure refinements. A rough estimation of the hypothetic phason instability temperature shows that it would be kinetically inaccessible and thus the phase transition to a 12 Å low T structure (at ~800 K) is most likely not phason-driven. Except for the obvious increase in the amplitude of the thermal motion, no other significant structural changes, in particular no sources of additional phason-related configurational entropy, were found. All structures are refined to very similar R-values, which proves that the quality of the refinement at each temperature is the same. This suggests, that concerning the stability factors, some QCs could be similar to other HT complex intermetallic phases. The experimental results clearly show that at least the ~4 Å structure of d-Al-Cu-Rh is a HT phase therefore entropy plays an important role in its stabilisation mechanism lowering the free energy. However, the main source of this entropy is probably not related to phason flips, but rather to lattice vibrations, occupational disorder unrelated to phason flips like split positions along the periodic axis.

Alterations of band 3 transport protein by cellular aging and disease: erythrocyte band 3 and glucose transporter share a functional relationship

1990 ◽  
Vol 68 (12) ◽  
pp. 1419-1427 ◽  
Author(s):  
Gieljan J. C. G. M. Bosman ◽  
Marguerite M. B. Kay
Keyword(s):  
Glucose Transport ◽  
Structural Changes ◽  
Glucose Transporter ◽  
Functional Relationship ◽  
Band 3 ◽  
Anion Transport ◽  
Cellular Aging ◽  
Abnormal Band ◽  
Membrane Spanning

Structural changes in human erythrocyte band 3 that affect anion transport are correlated with changes in glucose transport in situ. Breakdown of band 3, observed during normal erythrocyte aging in situ and in some diseases involving erythrocytes, is associated with an increase in Km and a decrease in Vmax of sulfate self-exchange, and with an increase in Km and Vmax of glucose efflux. Erythrocytes containing a high molecular weight form of band 3 exhibit an increase in Vmax of sulfate exchange and a decrease in Vmax of glucose efflux. Identical transport characteristics are observed in abnormal band-3-containing erythrocytes from individuals with familial amyotrophic chorea with acanthocytosis. A third band 3 alteration, fast-aging band 3, exhibits decreased Vmax of sulfate exchange and an increase in Km and decrease in Vmax of glucose efflux. Changes in band 3 structure that are the result of unstable hemoglobin or a deficiency in glucose-6-phosphate dehydrogenase and that do not affect anion transport have no effect on glucose transport characteristics. These data indicate the existence of a functional relationship between the membrane-spanning, anion-transport domain of band 3 and glucose transport in human erythrocytes. Antibodies to synthetic peptides reveal structural changes in membranes from the three inborn band 3 alterations and in band 3 itself in membranes from fast-aging band 3. Thus, immunological data suggests a structural relationship between anion and glucose transporters.Key words: red cell, anion transport, membrane proteins, aging, choreoacanthocytosis, anemia.

scholarly journals The Effect of Bile Salts on the Permeability and Ultrastructure of the Perfused, Energy-Depleted, Rat Blood-Brain Barrier

1991 ◽  
Vol 11 (4) ◽  
pp. 644-654 ◽  
Author(s):  
J. Greenwood ◽  
J. Adu ◽  
A. J. Davey ◽  
N. J. Abbott ◽  
M. W. B. Bradbury
Keyword(s):  
Blood Brain Barrier ◽  
Bile Salts ◽  
Structural Changes ◽  
Sodium Deoxycholate ◽  
Ringer Solution ◽  
Brain Barrier ◽  
Rat Blood ◽  
Blood Brain ◽  
Ultrastructural Damage

The action of bile salts upon the rat blood–brain barrier (BBB) was assessed in the absence of energy-yielding metabolism. Brains were perfused in situ with a Ringer solution for 5 min followed by a 1 min perfusion containing either sodium deoxycholate (DOC), taurochenodeoxycholate (TCDC), or Ringer/DNP. The integrity of the BBB was then determined by perfusing with the radiotracer [14C]mannitol for 2.5 min. Alternatively, the brains were perfusion fixed for ultrastructural assessment. At 0.2 m M DOC, the BBB remained intact and the cerebral ultrastructure was similar to the controls. At 1 m M and above, disruption of the BBB became evident. At 2 m M, the cerebral cortex became severely vacuolated, with damaged endothelium and collapsed capillaries. With TCDC, BBB disruption occurred at 0.2 m M without any apparent ultrastructural damage to the micro vasculature. Following 2 m M TCDC, similar, but less widespread, structural changes to the 2 m M DOC-perfused animals was apparent. Opening of the BBB occurred at a concentration lower than that required to cause lysis of either red blood cells or cultured cerebral endothelial cells. It is proposed that the effect of bile salts at concentrations of 1.5 m M and above is largely due to their lytic action as strong detergents on endothelial cell membranes, but that at lower concentrations a more subtle modification of the BBB occurs.

In situ XRD studies of the structural changes of ZrO2-coated LiCoO2 during cycling and their effects on capacity retention in lithium batteries

2006 ◽  
Vol 163 (1) ◽  
pp. 185-190 ◽  
Author(s):  
Kyung Yoon Chung ◽  
Won-Sub Yoon ◽  
Hung Sui Lee ◽  
James McBreen ◽  
Xiao-Qing Yang ◽  
...  
Keyword(s):  
Lithium Batteries ◽  
Structural Changes ◽  
Capacity Retention ◽  
In Situ Xrd ◽  
Xrd Studies
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