The thermal degradation of polyvinyl compounds. II. The degradation of benzoyl peroxide catalyzed polymethyl methacrylates

1949 ◽  
Vol 199 (1056) ◽  
pp. 14-23 ◽  
Keyword(s):  
Molecular Weight ◽  
Thermal Degradation ◽  
Benzoyl Peroxide ◽  
Molecular Size ◽  
Molecular Weights ◽  
Complete Degradation ◽  
Average Size

The thermal degradation of polymethyl methacrylates prepared by means of benzoyl peroxide has been investigated. The rate of monomer evolution is independent of molecular size for a given weight of polymer except that it falls off when the molecular weight approaches 500,000. Similarly at sufficiently low molecular weights the number of molecules in the tray of the still continuously decreases while the average size remains constant. These facts point to the mechanism’s involving the fission of the molecule into radicals, the fission occurring at the end of the molecule. Thereafter the large radical rapidly undergoes degradation, monomer units being evolved until the radical is completely removed. With the larger radicals there is not time for complete degradation; instead these interact by disproportionation and thus become stabilized.

Effect of extractant and molecular size on the optical and chemical properties of soil humic acids

Soil Research ◽  
1969 ◽  
Vol 7 (3) ◽  
pp. 229 ◽  
Author(s):  
JHA Butler ◽  
JN Ladd
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Humic Acids ◽  
Gel Filtration ◽  
Chemical Properties ◽  
Molecular Size ◽  
Carboxyl Content ◽  
Peptide Bonds ◽  
Molecular Weights ◽  
Amino Acid Contents

Humic acids extracted from soil with sodium pyrophosphate have greater proportions of lower molecular weight material, less acid-hydrolysable amino acid nitrogen contents, but greater carboxyl contents and extinction values (260 and 450 nm) than humic acids extracted subsequently from the same sample with alkali. Humic acids extracted with alkali from fresh soil samples have intermediate values. Extinction values at 260 nm are directly correlated with carboxyl contents for a given soil. Different crop histories have no significant effect on the measured properties of the extracted humic acids. An alkali-extracted humic acid has been fractionated by gel filtration into seven fractions of different nominal molecular weight ranges. As the molecular weights of the fractions increase, both aliphatic C-H (based on infrared absorption at 2900 cm-1) and acid-hydrolysable amino acid contents increase, whereas extinction values at 260 nm and carboxyl contents decrease. The infrared spectra of the high molecular weight fractions have peaks at 1650 and 1510 cm-1 which correlate with acid-hydrolysable amino acid contents and which correspond to amide I and II bands of peptide bonds. Alkaline hydrolysis to split peptide bonds eliminates both these peaks. The spectra also have peaks at 1720 and 1210 cm-1 which correlate with the carboxyl content.

scholarly journals Characterization of proteins from the cytoskeleton of Giardia lamblia

1983 ◽  
Vol 59 (1) ◽  
pp. 81-103 ◽  
Author(s):  
R. Crossley ◽  
D.V. Holberton
Keyword(s):  
Molecular Weight ◽  
Sodium Dodecyl Sulphate ◽  
Giardia Lamblia ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Molecular Size ◽  
Molecular Weights

Proteins from the axonemes and disc cytoskeleton of Giardia lamblia have been examined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. In addition to tubulin and the 30 X 10(3) molecular weight disc protein, at least 18 minor components copurify with the two major proteins in Triton-insoluble structures. The most prominent minor bands have the apparent molecular weights of 110 X 10(3), 95 X 10(3) and 81 X 10(3). Protein of 30 X 10(3) molecular weight accounts for about 20% of organelle protein on gels. In continuous 25 mM-Tris-glycine buffer it migrates mostly as a close-spaced doublet of polypeptides, which are here given the name giardins. Giardia tubulin and giardin have been purified by gel filtration chromatography in the presence of sodium dodecyl sulphate. Well-separated fractions were obtained that could be further characterized. Both proteins are heterogeneous when examined by isoelectric focusing. Five tubulin chains were detected by PAGE Blue 83 dye-binding after focusing in a broad-range ampholyte gel. Giardin is slightly less acidic than tubulin. On gels it splits into four major and four minor chains with isoelectric points in the pI range from 5.8 to 6.2. The amino acid composition of the giardin fraction has been determined, and compared to Giardia tubulin and a rat brain tubulin standard. Giardins are rich in helix-forming residues, particularly leucine. They have a low content of proline and glycine; therefore they may have extensive alpha-helical regions and be rod-shaped. As integral proteins of disc microribbons, giardins in vivo associate closely with tubulin. The properties of giardins indicate that in a number of respects - molecular size, charge, stoichiometry - their structural interaction with tubulin assemblies will be different from other tubulin-accessory protein copolymers studied in vitro.

Isoprene and Rubber. Part 29. High Molecular Hydrorubbers

1932 ◽  
Vol 5 (2) ◽  
pp. 136-140
Author(s):  
H. Staudinger ◽  
W. Feisst
Keyword(s):  
Molecular Weight ◽  
Catalytic Reduction ◽  
Molecular Form ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Rubber Part ◽  
Derivatives Of ◽  
Suitable Process

Abstract The molecular concept in organic chemistry is based upon the fact that the molecules, whose existence is proved by vapor density determinations, enter into chemical reactions as the smallest particles. If now it is assumed that organic molecular colloids like rubber are dissolved in dilute solution in molecular form then it must be proved that in the chemical transposition of macromolecules as well no change in the size of the macromolecules occurs. In the case of hemicolloids, therefore for molecular colloids with an average molecular weight of 1000 to 10,000, this has been proved by the reduction of polyindenes, especially of polysterenes, to hydroproducts with the same average molecular weight, and also by the fact that cyclorubbers do not change their molecular weight upon autoöxidation. The molecular weights of hemi-colloidal hydrocarbons are therefore invariable. This is much more difficult to prove in the case of rubber, although there are many more ways in which unsaturated rubber can be transposed than the stable polysterenes, polyindenes, and poly cyclorubbers. In most of the reactions with rubber, as in its action with nitrosobenzene, oxidizing agents, hydrogen halides, and halogens, an extensive decomposition takes place as a result of the instability of the molecule, which is referred to in another work. Therefore derivatives of rubber are not formed, but derivatives of hemi-colloidal decomposition products. The catalytic reduction of rubber in the cold appears to be the most suitable process of making it react without changing its molecular size in order to prove that in a chemical transposition its molecular weight remains the same.

scholarly journals Investigation of Molecular Size Effect on the Formation of Lignin Nanoparticles by Nanoprecipitation

2020 ◽  
Vol 10 (14) ◽  
pp. 4910
Author(s):  
Jae Hoon Lee ◽  
Shin Young Park ◽  
In-Gyu Choi ◽  
Joon Weon Choi
Keyword(s):  
Polymeric Nanoparticles ◽  
Drug Carrier ◽  
Particle Surface ◽  
Molecular Size ◽  
Remarkable Change ◽  
Molecular Weights ◽  
Chemical Structures ◽  
Potential Applications ◽  
Soda Lignin ◽  
Average Size

In recent years, several studies focused on the synthesis of lignin-based nanoparticle in aqueous solution and its potential applications of the drug carrier were investigated. In this study, soda lignin (SL) nanoparticles (i.d. 128–560 nm) were synthesized by the nanoprecipitation process at three different concentrations (1, 2, and 4 mg/mL THF) with various molecular sizes of soda lignin (NP-F1, NP-F2, and NP-F3) obtained from sequential solvent extraction. The average molecular weights of SL, F1, F2, F3, F4, and F5 were 3130, 1190, 2550, 3680, 5310, and 14,650, respectively. The average size of the spherical lignin nanoparticle was a minimum of 128 nm for NP-C1 and the size increased up to 560 nm with increasing concentration. Particle surface charge increased with increasing concentration from −26 mV for NP-C1 to −38 mV for NP-C4. Contrary to expected general trends in polymeric nanoparticles, there was no remarkable change or trend with increasing lignin molecular weight since chemical structures of each lignin fraction are also remarkably different. Further studies to learn correlation between properties of lignin nanoparticle and its additional details regarding the chemical structures is needed.

Equilibrium Molecular Weight Distribution of Cyclic and Linear Methylsiloxanes

1967 ◽  
Vol 40 (4) ◽  
pp. 1084-1093 ◽  
Author(s):  
Jack B. Carmichael ◽  
James Heffel
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Equilibrium Constants ◽  
Molecular Size ◽  
Size Distributions ◽  
Flory Theory ◽  
Molecular Weights ◽  
Cyclic Molecules

Abstract Data are reported for the equilibrium molecular size distributions of cyclic and linear methylsiloxanes in five polymers with number average molecular weights ranging from 459 to 1348. The distributions of linear species agree with the earlier work of Scott and agree reasonably well with the Flory theory of random reorganization. The amounts of cyclic molecules are sharply dependent on molecular weight. However, the equilibrium constants for cyclic formation for cyclic species with four to eight units are shown to be virtually identical with the equilibrium constants for cyclic formation in high molecular weight polymers reported in a previous publication. For octamethylcyclotetrasiloxane, Kav in moles of siloxane units per liter was found to be 0.72 in this study. For high polymers, Kav was previously reported to be 0.74.

scholarly journals Effect of molecular size of 125I-labelled poly(vinylpyrrolidone) on its pinocytosis by rat visceral yolk sacs and rat peritoneal macrophages

1981 ◽  
Vol 196 (1) ◽  
pp. 49-55 ◽  
Author(s):  
R Duncan ◽  
M K Pratten ◽  
H C Cable ◽  
H Ringsdorf ◽  
J B Lloyd
Keyword(s):  
Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Cell Types ◽  
Peritoneal Macrophages ◽  
Yolk Sac ◽  
High Molecular Weight Fraction ◽  
Molecular Weights ◽  
Molecular Weight Distributions

Rates of pinocytosis of different molecular-weight distributions of 125I-labelled poly(vinylpyrrolidone) by rat visceral yolk sacs and rat peritoneal macrophages were measured in vitro. Four preparations of mean molecular weights 50 000, 84 000, 700 000 and 7 000 000, were used. Macrophages captured the highest-molecular-weight preparation more rapidly than the other preparations. In contrast, rate of capture by the yolk sac decreased with increasing molecular weight. Incubations with a very-high-molecular-weight fraction derived from the 7 000 000-average-mol. wt. preparation clearly demonstrated that very large polymer molecules are not accumulated by the yolk sac, but are preferentially captured by macrophages. Analysis of the 125I-labelled poly(vinylpyrrolidone) internalized by the two cell types confirmed that low-molecular-weight material is preferred by the yolk sac, whereas the macrophage is less discriminating.

The thermal degradation of polyvinyl compounds IV. The thermal degradation of the methyl methacrylate copolymers with glycol dimethacrylate and acrylonitrile

1949 ◽  
Vol 199 (1056) ◽  
pp. 39-55 ◽  
Keyword(s):  
Molecular Weight ◽  
Thermal Degradation ◽  
Methyl Methacrylate ◽  
The Other ◽  
Glycol Dimethacrylate ◽  
Acrylonitrile Copolymer ◽  
Molecular Weights ◽  
Quantitative Calculation ◽  
Methacrylate Copolymers ◽  
Cross Links

The effect upon degradation of cross-links, formed by copolymerizing small amounts of glycol dimethacrylate with the methyl methacrylate, and small amounts of acrylonitrile units in the chains has been investigated. Cross-links make no difference to the degradation characteristics according to rate measurements. Molecular weights could not be measured in this case owing to the insolubility of the polymer. The methyl methacrylate-acrylonitrile copolymer degrades in quite a different way from polymer composed of homogeneous methyl methacrylate chains. In this case the chain ruptures initially at or near the acrylonitrile units, the molecular weight falling very rapidly in the initial stages of the reaction. One side of the break is terminated by an acrylonitrile unit which cannot degrade but the other side may sooner or later degrade to the next acrylonitrile unit along the chain. The induction period observed is probably due to the time taken to build up an appreciable concentration of such degradable ends. A quantitative calculation agrees well with this theory.

Separation of Sub-Units of Antihemophilic Factor (AHF) by Agarose Gel Chromatography

1972 ◽  
Vol 27 (02) ◽  
pp. 212-219 ◽  
Author(s):  
H. J Weiss ◽  
Louise L. Phillips ◽  
W. Rosner
Keyword(s):  
Molecular Weight ◽  
Molecular Size ◽  
Void Volume ◽  
Gel Chromatography ◽  
Agarose Gel ◽  
Major Peak ◽  
Molecular Weights ◽  
Congenital Afibrinogenemia ◽  
Weight Substance ◽  
Antihemophilic Factor

SummaryThe molecular weight of antihemophilic factor (AHF) in plasma and cryoprecipitate was studied by chromatography on agarose gel (Bio-Gel A, 1.5 M). At a pH of 7.4 and the ionic strength of plasma, AHF appeared in the void volume as a sharp, symmetrical peak, indicating a molecular weight of 1.5 million or greater. Similar findings were obtained in a patient with congenital afibrinogenemia. At a pH of 7.7, the major peak of AHF-activity was again found in the void volume, but a spreading of activity into higher elution volumes was also observed. In 1 M NaCl, pH 7.4, AHF dissociated into active sub-units of varying molecular size. The molecular weights of the smallest subunits were estimated to be 169,000-194,000. These studies provide further evidence that AHF is a high molecular weight substance, not associated with fibrinogen, whose quarternary structure may be disrupted to produce active sub-units of varying sizes.

Carboxylesterases (EC 3.1.1). The Molecular Sizes of Chicken and Pig Liver Carboxylesterases

1975 ◽  
Vol 53 (5) ◽  
pp. 547-560 ◽  
Author(s):  
Peter A. Inkerman ◽  
Donald J. Winzor ◽  
Burt Zerner
Keyword(s):  
Molecular Weight ◽  
Equilibrium Constants ◽  
Polyacrylamide Gel Electrophoresis ◽  
Molecular Size ◽  
Chicken Liver ◽  
Velocity Sedimentation ◽  
Pig Liver ◽  
Molecular Weights ◽  
Equilibrium Sedimentation ◽  
Ca 50

The molecular size of pig liver carboxylesterase has been investigated under a variety of conditions of pH and ionic strength. From equilibrium and velocity sedimentation at pH 4.0 and pH 7.5, and from chromatography on Sephadex G-200, we conclude that the monomeric molecular weight is ~65 000 daltons and that the enzyme associates to form trimers. Association equilibrium constants for the monomer–trimer system were estimated to be 0.02 l2 g−2 at pH 4 (concentration-dependent molecular weight data) and 2 × 105 l2 g−2 at pH 7.5 (frontal gel chromatographic results). These studies were aided by comparisons of the properties of the pig liver enzyme with those of chicken liver carboxylesterase, which is shown to exhibit the velocity and equilibrium sedimentation characteristics of a homogeneous protein with molecular weight ~65 000. Studies of pig and chicken liver carboxylesterases in 6 M guanidinium chloride, 0.1 M in β-mercaptoethanol, support the proposition that the monomeric species of these enzymes have molecular weights of ~65 000. On polyacrylamide gel electrophoresis in SDS, there is no evidence for a major species of molecular weight less than ~65 000 for the pig enzyme, but ca. 50% of the chicken esterase is dissociated into two species of molecular weight ~30 000.

Molecular Size of the Diapause Hormone of the Silkworm Bombyx mori

1976 ◽  
Vol 31 (3-4) ◽  
pp. 132-134 ◽  
Author(s):  
Ichiro Kubota ◽  
Minoru Isobe ◽  
Toshio Goto ◽  
Kinsaku Hasegawa
Keyword(s):  
Molecular Weight ◽  
Bombyx Mori ◽  
Organic Solvents ◽  
Molecular Size ◽  
Gel Permeation Chromatography ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Modified Peptides ◽  
Diapause Hormone ◽  
Silkworm Bombyx Mori

Abstract The diapause hormone (D H) responsible for arrested development of the silkworm Bombix mori consists of two active principles of peptide (A and B) . Since both hormones form aggregates in aqueous phases, the molecular weights were determined by gel permeation chromatography of Merckogel OR 6000 using methanol-dichloromethane mixture as the developing agent. Gramicidins and modified peptides soluble in the organic solvents were used as the standard markers for the molecular weight measurements of the hormones. The molecular weights of DH -A and -B are estimated to be 3300 ± 400 and 2000 ± 200, respectively.

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