The Molecular Weights of Rubber and Related Materials: I. Experimental Methods

1942 ◽  
Vol 15 (1) ◽  
pp. 43-59
Author(s):  
G. Gee
Keyword(s):  
Molecular Weight ◽  
Sol Gel ◽  
Experimental Methods ◽  
Viscosity Data ◽  
Molecular Weight Range ◽  
Molecular Weights ◽  
Molecular Weight Difference ◽  
Small Factor ◽  
Osmotic Behavior ◽  
Poor Solvent

Abstract The osmotic molecular weight of crepe has been measured in several solvents. It is shown that the use of a poor solvent, or a mixture of solvent and precipitant, gives solutions which approach ideal osmotic behavior. Benzene containing 150 cc. of methanol per liter is the best solvent examined, 1 per cent solutions of crepe being almost ideal. Viscosity data are employed to calculate absolute weight average molecular weights, the Staudinger constant being determined by comparison with ultracentrifuge data. Constants are listed for a number of solvents, and shown to vary only by a small factor. The osmotic and viscosity molecular weights of a number of rubbers are compared; the two values agree for three rubber fractions, while for unfractionated materials the viscosity average is the higher. Non-uniformity coefficients are calculated from the ratio of the two molecular weights. The molecular weight of sol rubber is higher than that of gel, showing that the sol-gel separation does not arise from molecular weight difference. The Staudinger law is shown to hold for rubber solutions at least over the molecular weight range 350,000–60,000, and probably very much further.

scholarly journals Nuclear matrix of HeLa S3 cells. Polypeptide composition during adenovirus infection and in phases of the cell cycle.

1977 ◽  
Vol 72 (1) ◽  
pp. 194-208 ◽  
Author(s):  
L D Hodge ◽  
P Mancini ◽  
F M Davis ◽  
P Heywood
Keyword(s):  
Cell Cycle ◽  
Molecular Weight ◽  
Nuclear Matrix ◽  
Apparent Molecular Weight ◽  
Molecular Weight Range ◽  
Weight Range ◽  
Molecular Weights ◽  
Liver Nuclei ◽  
Hela S3 ◽  
Biochemical Analyses

A subnuclear fraction has been isolated from HeLa S3 nuclei after treatment with high salt buffer, deoxyribonuclease, and dithiothreitol. This fraction retains the approximate size and shape of nuclei and resembles the nuclear matrix recently isolated from rat liver nuclei. Ultrastructural and biochemical analyses indicate that this structure consists of nonmembranous elements as well as some membranous elements. Its chemical composition is 87% protein, 12% phospholipid, 1% DNA, and 0.1% RNA by weight. The protein constituents are resolved in SDS-polyacrylamide slab gels into 30-35 distinguishable bands in the apparent molecular weight range of 14,000 - 200,000 with major peptides at 14,000 - 18,000 and 45,000 - 75,000. Analysis of newly synthesized polypeptides by cylindrical gel electrophoresis reveals another cluster in the 90,000-130,000 molecular weight range. Infection with adenovirus results in an altered polypeptide profile. Additional polypeptides with apparent molecular weights of 21,000, 23,000, and 92,000 become major components by 22 h after infection. Concomitantly, some peptides in the 45,000-75,000 mol wt range become less prominent. In synchronized cells the relative staining capacity of the six bands in the 45,000-75,000 mol wt range changes during the cell cycle. Synthesis of at least some matrix polypeptides occures in all phases of the cell cycle, although there is decreased synthesis in late S/G2. In the absence of protein synthesis after cell division, at least some polypeptides in the 45,000-75,000 mol wt range survive nuclear dispersal and subsequent reformation during mitosis. The possible significance of this subnuclear structure with regard to structure-function relationships within the nucleus during virus replication and during the life cycle of the cell is discussed.

Molecular Weights and Intrinsic Viscosities of Polyisobutylenes

1943 ◽  
Vol 16 (3) ◽  
pp. 493-508
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Chain Structure ◽  
Molecular Weight Range ◽  
Molecular Weights ◽  
Satisfactory Precision ◽  
Heterogeneous Polymers ◽  
Definition Of

Abstract Experimental methods for fractionating polyisobutylene and for determining osmotic pressures have been described. The ratio π/c of osmotic pressure to concentration has been found in the case of cyclohexane solutions of polyisobutylene to vary nonlinearly with concentration, contrary to recent theories advanced by Huggins and the writer. The slope of this relationship appears to be independent of molecular weight. Reliable methods for extrapolating π/c to c=0 have been established, enabling the determination of absolute molecular weights with satisfactory precision up to values of about 1,000,000. Molecular weights of polyisobutylenes calculated from Staudinger's equation are too low; the discrepancy is more than ten-fold at high molecular weights. On the basis of data for carefully fractionated samples covering a two-hundred-fold molecular weight range, the intrinsic viscosity is found to be proportional to the 0.64 power of the molecular weight. This decided deviation from Staudinger's “law”cannot in this instance be attributed to nonlinear chain structure, as Staudinger has sought to do in other cases. This dependence of molecular weight on intrinsic viscosity leads to the definition of a “viscosity average”molecular weight which is obtained when the relationship is applied to heterogeneous polymers. The viscosity average is less than the weight average molecular weight, which would be obtained if Staudinger's equation were applicable, and greater than the number average obtained by osmotic or cryoscopic methods.

The direct observation of polymer molecules and determination of their molecular weight

1964 ◽  
Vol 279 (1376) ◽  
pp. 50-61 ◽  
Keyword(s):  
Molecular Weight ◽  
Direct Observation ◽  
Particle Diameter ◽  
Dilute Solution ◽  
Crystalline Polymers ◽  
Polymer Molecules ◽  
Molecular Weights ◽  
Preferential Evaporation ◽  
Poor Solvent

An experimental investigation of the conditions necessary for the production of compact, single polymer molecules, in a form suitable for direct observation in the electron microscope, is described. Molecules are isolated by dispersing a dilute solution of the polymer as fine droplets on to a suitable substrate: ideally each droplet should contain either one or no polymer molecules. The solution is a mixture of two solvents, a good one and a poor one. Initially the good solvent predominates so that the probability of polymer aggregation is low. Preferential evaporation of the relatively volatile solvent on the substrate itself gives the poor solvent conditions needed for the formation of well-defined molecular spheres. Factors determining the choice of solvent, precipitant, and the composition of the mixture are discussed. There is little difficulty in obtaining single molecules with glassy amorphus polymers; rubbery polymers collapse and spherical molecules are formed only if the entire preparation is carried out at a temperature below that of the glass transition; crystalline polymers are not amenable to this technique. To obtain sufficient contrast the particles have to be shadowed and it is shown that, although certain dimensions are distorted by the metal coating, the shadow length faithfully represents the true particle diameter. Molecular weights, and their distribution, when of the order of a million and above, can readily be accurately determined. Conventional methods are unreliable in this region of high molecular weight.

Molecular Weight Effects in Adsorption of Rubbers on Carbon Black

1968 ◽  
Vol 41 (5) ◽  
pp. 1256-1270 ◽  
Author(s):  
Gerard Kraus ◽  
J. T. Gruver
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Large Particle ◽  
Molecular Weights ◽  
Molecular Weight Dependence ◽  
Bound Rubber ◽  
Sieve Effect ◽  
High Structure ◽  
Very High ◽  
Poor Solvent

Abstract The molecular weight dependence of the adsorption of polybutadiene on carbon black from a poor solvent, n-heptane, and bulk, i.e., the phenomenon of “bound rubber”, was investigated. For narrow distribution polymers the adsorption is proportional to Mn, where n = 0.14 for adsorption from n-heptane solution; n = 0.5 for adsorption from bulk. Anomalously low solution adsorption was observed for polymers of very high molecular weight (> 500,000). This is ascribed to a sieve effect by aggregates of carbon black particles which cannot be penetrated by the large molecular coils. In high structure blacks, which pack more loosely, and in large particle blacks, which form larger interstices between particles, onset of anomalous adsorption is shifted toward higher molecular weights.

Chromatographic Fractionation of Some Synthetic Elastomers

1948 ◽  
Vol 21 (3) ◽  
pp. 682-683 ◽  
Author(s):  
Ivan Landler
Keyword(s):  
Molecular Weight ◽  
Cellulose Acetate ◽  
Active Carbon ◽  
Low Molecular Weight ◽  
High Polymer ◽  
Acrylonitrile Copolymer ◽  
Molecular Weights ◽  
The Mean ◽  
Mean Molecular Weight ◽  
Poor Solvent

Abstract Mark and Saito were the first to fractionate a high polymer (cellulose acetate) by chromatographic adsorption on blood carbon. They found that molecules of low molecular weight were adsorbed first, and that the mean molecular weight of the product which remained unadsorbed was higher than the original molecular weight. Levi and Giera confirmed this result, but did not succeed in fractionating Buna-S or polyisoprene, for these polymers were eluted by the solvent during the washing operation in the column. The present authors have carried out further experiments in this field with a study of three commercial synthetic elastomers, viz., GR-S (butadienestyrene copolymer), Perbunan-N (butadiene-acrylonitrile copolymer), and Visitanex (polyisobutylene). The polymer was adsorbed by starting with a poor solvent composed of a mixture of toluene and methanol ; the quantity of alcohol added was just below the threshold of precipitation. The adsorbent used was a mixture of 75 per cent of lamp black (80 square meters per gram) and 25 per cent of coarse active carbon. The latter served to prevent agglomeration of the lamp black. The adsorbent was divided into three layers, of 10 grams each. At the end of the tube was a filter of fritted glass. Filtration was carried out under pressure, the rate of flow thereby being maintained constant, The polymers were characterized by their intrinsic viscosities. The molecular weights which were estimated by means of the relation, found experimentally between the molecular weight and viscosity, are only approximate, for this relation holds true only for narrow fractions.

THE MOLECULAR WEIGHT OF POLYVINYL ACETATE

1958 ◽  
Vol 36 (3) ◽  
pp. 543-549 ◽  
Author(s):  
A. F. Sirianni ◽  
R. Tremblay ◽  
I. E. Puddington
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
Polyvinyl Acetate ◽  
Molecular Weight Range ◽  
Weight Range ◽  
Molecular Weights ◽  
Approximate Molecular Weight ◽  
Low Degrees ◽  
Made In

The molecular weights of a series of unfractionated polyvinyl acetates of low degrees of polymerization have been measured by determining the lowering of the vapor pressure of their solutions. An approximate molecular-weight range of 5000–40,000 was examined. While most of the determinations were made in benzene solutions at 55 °C., other solvents and temperatures were used. Anomalous results were obtained with one sample of fractionated material.

Effects of poly(ethylene glycol) additive molecular weight on the microstructure and properties of sol-gel-derived lead zirconate titanate thin films

2003 ◽  
Vol 18 (3) ◽  
pp. 737-741 ◽  
Author(s):  
Shuhui Yu ◽  
Kui Yao ◽  
Santiranjan Shannigrahi ◽  
Francis Tay Eng Hock
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Ethylene Glycol ◽  
Lead Zirconate Titanate ◽  
Sol Gel ◽  
Lead Zirconate ◽  
Poly Ethylene Glycol ◽  
Molecular Weights ◽  
Zirconate Titanate ◽  
Poly Ethylene

Poly(ethylene glycol) (PEG) additives with different molecular weights were used to modify sol-gel precursor solutions for preparing lead zirconate titanate (PZT) thin films. The morphology, crystalline structure, and mechanical and electrical properties of the films were characterized. The relationship between the characteristics of the films and the molecular weight of PEG was investigated. It was observed that the PEG eliminated cracking of the films during multiple pyrolysis treatments. However, with the increase of the PEG molecular weight, the films became less dense, which led to decreased Young's modulus and dielectric constant and increased coercive field. Our experiments showed that films prepared from sols modified by PEG with a molecular weight of 200 exhibited a dense morphology and excellent mechanical and electric properties without cracking.

Monoclonal Antibody Specific to a Major Fish Allergen: Parvalbumin

2009 ◽  
Vol 72 (4) ◽  
pp. 818-825 ◽  
Author(s):  
KAMIL G. GAJEWSKI ◽  
YUN-HWA P. HSIEH
Keyword(s):  
Molecular Weight ◽  
Monoclonal Antibody ◽  
Western Blot ◽  
Fish Species ◽  
Heat Stability ◽  
Enzyme Linked Immunosorbent Assay ◽  
Molecular Weight Range ◽  
Antigenic Protein ◽  
Binding Characteristics ◽  
Molecular Weights

The major fish allergen, parvalbumin, is a low-molecular-weight (10 to 13 kDa), heat-stable protein. Monoclonal antibody (MAb) 3E1, developed against heat-treated catfish sarcoplasmic protein extract, recognizes a thermal-stable protein with the molecular-weight range of parvalbumin in fish extracts. We further investigated the antigen-binding characteristics of this antibody by comparing its immunoreactivity against various fish and other animal species, with a commercially available anti-parvalbumin antibody, MAb PARV-19. Soluble proteins were extracted from 67 cooked (100°C for 20 min) finfish, shellfish, meat, and poultry species. Indirect enzyme-linked immunosorbent assay (ELISA) was performed to examine the immunore-activity of both MAb 3E1 and MAb PARV-19 with sample extracts. Western blot was performed to compare the antigenic protein banding patterns in cooked fish extracts by using these two MAbs. The ELISA results revealed that both MAbs had identical reaction patterns to the fish species tested. Removal of Ca2+ from the fish extracts increased the overall immunore-activity of both MAbs. Western blot results confirmed that the antigenic protein banding pattern in various fish species blotted by MAb 3E1 corresponded to the molecular weights of parvalbumins recognized by PARV-19. However, screening with nonfinfish extracts revealed MAb 3E1 to be strictly finfish specific, while PARV-19 cross-reacted with frog, rat, and rabbit extracts. Based on the heat stability, molecular weight, immunoreactivity, and Ca2+-dependent binding of the antigenic proteins, MAb 3E1 is specific to fish parvalbumin. It would therefore be a useful probe for investigating the major fish allergen in both raw and processed food.

Direct Observations of Polymer Molecules and Determination of their Molecular Weight

1966 ◽  
Vol 39 (3) ◽  
pp. 567-580
Author(s):  
M. J. Richardson
Keyword(s):  
Molecular Weight ◽  
Particle Diameter ◽  
Dilute Solution ◽  
Crystalline Polymers ◽  
Polymer Molecules ◽  
Molecular Weights ◽  
Direct Observations ◽  
Preferential Evaporation ◽  
Poor Solvent

Abstract An experimental investigation of the conditions necessary for the production of compact, single polymer molecules, in a form suitable for direct observation in the electron microscope, is described. Molecules are isolated by dispersing a dilute solution of the polymer as fine droplets on to a suitable substrate: ideally each droplet should contain either one or no polymer molecules. The solution is a mixture of two solvents, a good one and a poor one. Initially the good solvent predominates so that the probability of polymer aggregation is low. Preferential evaporation of the relatively volatile solvent on the substrate itself gives the poor solvent conditions needed for the formation of well-defined molecular spheres. Factors determining the choice of solvent, precipitant, and the composition of the mixture are discussed. There is little difficulty in obtaining single molecules with glassy amorphous polymers; rubbery polymers collapse and spherical molecules are formed only if the entire preparation is carried out at a temperature below that of the glass transition; crystalline polymers are not amenable to this technique. To obtain sufficient contrast the particles have to be shadowed and it is shown that, although certain dimensions are distorted by the metal coating, the shadow length faithfully represents the true particle diameter. Molecular weights, and their distribution, when of the order of a million and above, can readily be accurately determined. Conventional methods are unreliable in this region of high molecular weight.

scholarly journals The solubility of fibrinogen in solutions containing dextrans of various molecular weights (Short Communication)

1974 ◽  
Vol 143 (3) ◽  
pp. 767-769 ◽  
Author(s):  
Michael W. Rampling
Keyword(s):  
Molecular Weight ◽  
Short Communication ◽  
Molecular Weight Range ◽  
Weight Range ◽  
Molecular Weights ◽  
Steric Exclusion

The effect of dextrans of various molecular weights on the solubility of fibrinogen was investigated. The results indicate that the prime effect responsible for the observed changes of solubility was steric exclusion. This applies over the whole molecular-weight range of dextrans used, i.e. from 5700 to 76000.

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