Thermomechanical Characterization of the Molecular Weight of Linear Polymers Exemplified by Natural Rubber

1964 ◽  
Vol 37 (1) ◽  
pp. 99-102
Author(s):  
B. Ya Teitelbaum ◽  
K. F. Gubanov
Keyword(s):  
Molecular Weight ◽  
Experimental Studies ◽  
Thermomechanical Properties ◽  
Linear Polymers ◽  
Molecular Weights ◽  
Calculated Molecular Weight ◽  
Low Degree ◽  
Wide Range ◽  
High Elasticity

Abstract In the previous work of Kargin and Slonimskii and that of Kargin and Sogolov who studied the behavior of polymers over a wide range of temperature, it was shown that the shape of thermomechanical curves depends on magnitude of molecular weight of the polymers. As a result of investigation of theory and actual experimental studies in which polyisobutylene was employed, it was demonstrated that molecular weight could be estimated on the basis of thermomechanical properties. This suggested a relationship between the magnitude of molecular weight M found from the thermomechanical curves and that which was determined from glass temperatures Tg and fluid temperatures Tf. For practical use of this relationship, it is necessary to know the magnitude of the segments and two empirical constants. These values can be found by calculation of molecular weights of three different fractions of the polymer. This can be accomplished experimentally by any independent method. Once these magnitudes are determined, it is necessary to find, by means of the thermomechanical curve, the values Tg and Tf, in order to calculate the molecular weight of any sample of the same polymer. Because of the low degree of accuracy of determination of these values, and because of the peculiar differences, the reliability of the calculated molecular weight cannot be great, especially since the equation utilizes the logarithm of the molecular weight figure and not the molecular weight itself. Apparently the graphic solution is simpler than analytical methods: by means of the data of thermomechanical studies for various fractions of known molecular weights it is possible to graph the dependence of M or log Mon Tf−Tg. From what has been said, it is evident that we may use the demonstrated method only for polymers of high elasticity, and furthermore, only for those fractions in which Tf−Tg is greater than zero.

scholarly journals Determination of polymeric functional additives in diesel fuel by gel penetration chromatography

2021 ◽  
Vol 25 (1) ◽  
pp. 53-62
Author(s):  
Yu. A. Ivanova ◽  
◽  
Z. A. Temerdashev ◽  
I. A. Kolychev ◽  
N. V. Kiseleva ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Diesel Fuel ◽  
Solid Phase ◽  
Chromatographic System ◽  
Molecular Weights ◽  
Functional Additives ◽  
Molecular Weight Characteristics ◽  
Wide Range ◽  
Dispersant Additive

Current article is devoted to the development of a method for determining polymer functional additives and their molecular weight characteristics in diesel fuel by gel penetration chromatography. The objects of the study were solutions of “C5A”, “Maxoil D”, “Detersol”, polymethymethacrylate “D” (PMAD), “Keropur D ”, Antigel “Difron 3319” and “Superantigel” individual additives as well as the diesel fuel produced by the “Kuban Oil and Gas Company - Ilskiy Oil Refinery”, LLC. The conditions for chromatographic separation and determination of polymeric functional additives were determined considering the analyzed fuel matrix, the working range of the separated masses and molecular weights of analytes, and the composition of the eluent applicable for wide range of analytes. The chromatographic system was calibrated using the narrowly dispersed analytical standard polystyrene samples with molecular weights of 1000, 2000, 4000, 10000, 30,000, 50,000, and 70,000 Da respectively. The molecular weight characteristics were calculated for each functional additive from the analytical standard samples of polystyrene. The method of GPC determination of polymeric functional additives in diesel fuel, along with the concentration characteristics, also makes it possible to determine the molecular weight parameters of wide range of polymeric functional additives; therefore, it is promising for monitoring the quality of the diesel fuel. The proposed analytical scheme was tested in the analysis of real sample of diesel fuel. The GPC scheme for the determination of the “Keroflux 3699” depressant-dispersant additive in diesel fuel included sample preparation using the solid-phase extraction, calibration of the chromatographic system using the standard polystyrene samples, GPC determination of additive components, and the calculation of molecular weight characteristics. The molecular weight characteristics of the “Keroflux 3699” depressant dispersant additive in diesel fuel have been established - the number average and weight average molecular weights equivalent to polystyrene were 10,300 and 8800 Da respectively, and the polydispersity index of the additive was 1.17.

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

EFFECTS OF FRESH PLASMA OR WHOLE BLOOD TRANSFUSIONS ON PATIENTS WITH VARIOUS TYPES OF MUCOPOLYSACCHARIDOSIS

PEDIATRICS ◽  
1972 ◽  
Vol 50 (5) ◽  
pp. 688-692
Author(s):  
Anatole S. Dekaban ◽  
Kenton R. Holden ◽  
George Constantopoulos
Keyword(s):  
Molecular Weight ◽  
Weight Distribution ◽  
Whole Blood ◽  
Blood Transfusions ◽  
Molecular Weights ◽  
The Third ◽  
Clinical Observations ◽  
Before And After ◽  
Fresh Plasma

Repeated fresh plasma or whole blood transfusions were given to five patients with either Hurler, Hunter, or Sanfilippo types of mucopolysaccharidosis. Clinical observations and total 24-hour urinary AMPS and their composition and molecular weight distribution were determined before, during, and after transfusions. The two patients who received plasma transfusions showed no noticeable change in the amount of AMPS excreted; of the three patients who received whole blood transfusions, two had slightly less excretion of AMPS while the third showed no difference. The AMPS in the CSF were measured in one patient before and after blood transfusions and found to be unchanged; likewise, the determination of molecular weights in the isolated AMPS was virtually identical. In the patients studied, the transfusions caused no demonstrable difference in the patients' clinical condition.

scholarly journals Evolutionary Steps in the Analytics of Primordial Metabolic Evolution

Life ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 50 ◽  
Author(s):  
Thomas Geisberger ◽  
Philippe Diederich ◽  
Thomas Steiner ◽  
Wolfgang Eisenreich ◽  
Philippe Schmitt-Kopplin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Isotope Labeling ◽  
Simultaneous Detection ◽  
Experimental Studies ◽  
Structural Determination ◽  
Metabolic Evolution ◽  
Analytical Procedures ◽  
Targeted Approach

Experimental studies of primordial metabolic evolution are based on multi-component reactions which typically result in highly complex product mixtures. The detection and structural assignment of these products crucially depends on sensitive and selective analytical procedures. Progress in the instrumentation of these methods steadily lowered the detection limits to concentrations in the pico molar range. At the same time, conceptual improvements in chromatography, nuclear magnetic resonance (NMR) and mass spectrometry dramatically increased the resolution power as well as throughput, now, allowing the simultaneous detection and structural determination of hundreds to thousands of compounds in complex mixtures. In retrospective, the development of these analytical methods occurred stepwise in a kind of evolutionary process that is reminiscent of steps occurring in the evolution of metabolism under chemoautotrophic conditions. This can be nicely exemplified in the analytical procedures used in our own studies that are based on Wächtershäuser’s theory for metabolic evolution under Fe/Ni-catalyzed volcanic aqueous conditions. At the onset of these studies, gas chromatography (GC) and GC-MS (mass spectrometry) was optimized to detect specific low molecular weight products (<200 Da) in a targeted approach, e.g., methyl thioacetate, amino acids, hydroxy acids, and closely related molecules. Liquid chromatography mass spectrometry (LC-MS) was utilized for the detection of larger molecules including peptides exceeding a molecular weight of 200 Da. Although being less sensitive than GC-MS or LC-MS, NMR spectroscopy benefitted the structural determination of relevant products, such as intermediates involved in a putative primordial peptide cycle. In future, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) seems to develop as a complementary method to analyze the compositional space of the products and reaction clusters in a non-targeted approach at unprecedented sensitivity and mass resolution (700,000 for m/z 250). Stable isotope labeling was important to differentiate between reaction products and artifacts but also to reveal the mechanisms of product formation. In this review; we summarize some of the developmental steps and key improvements in analytical procedures mainly used in own studies of metabolic evolution.

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.

Elastic Deformation and Molecular Weight in Polyisobutylene

1946 ◽  
Vol 19 (4) ◽  
pp. 1047-1050
Author(s):  
John Rehner
Keyword(s):  
Molecular Weight ◽  
Parallel Plate ◽  
Compressive Load ◽  
Published Data ◽  
Fractional Powers ◽  
Rapid Procedure ◽  
Molecular Weights ◽  
High Elasticity ◽  
Polymer Dissolution ◽  
Straight Lines

Abstract Although various properties of high polymers are known to depend on molecular weight, there appear to be no published data which show explicitly how the molecular weight of a rubber-like substance influences the modulus of high elasticity, even though a psychological perception of some such relationship has long existed. Also, the various expressions that have been derived by statistical methods contain molecular weight as a factor ranging from an inverse first power up to inverse higher fractional powers. Some time ago a need arose in this laboratory for estimating the average molecular weights of samples of polyisobutylene by a rapid procedure. Because of the slowness of polymer dissolution, methods based on measurements of the polymer in the dissolved state had to be ruled out and an investigation was, therefore, made of the rate of compression of a variety of samples in a Williams parallel-plate plastometer. It was found possible to render negligible the viscous component of deformation by using a sufficiently high compressive load and by limiting readings to an interval of about one minute. When the observed deformation values were plotted against the logarithm of time, straight lines were obtained. The slopes of the lines could be correlated, at least approximately, linearly with the reciprocal average molecular weights of the samples.

Measurement of the Isothermal Volume Dilation Accompanying the Unilateral Extension of Rubber

1959 ◽  
Vol 32 (2) ◽  
pp. 428-433
Author(s):  
Fred G. Hewitt ◽  
Robert L. Anthony
Keyword(s):  
Molecular Weight ◽  
Young’S Modulus ◽  
Experimental Results ◽  
Molecular Weights ◽  
Rubber Specimen ◽  
A Value ◽  
Fractional Increase ◽  
Internal Agreement ◽  
Good Agreement

Abstract The fractional increase in volume accompanying the isothermal extension of soft gum rubber was measured for four rubber samples at mean extensions of 14, 33, and 51%. The chain molecular weights Mc of the four samples were 5500, 5100, 4400, and 3000, with an estimated uncertainty of about 10% in each value of Mc. The observed fractional increase in volume ranged from 3.2×10−5 to 142×10−5, the latter value being observed for the sample of lowest chain molecular weight and at the extension of 51%. The experimental results for each sample have been represented by theoretical curves based on Gee's expression for the fractional increase in volume as a function of the sample extension. The theoretical curves exhibit good agreement with those of Gee, Stern, and Treloar. The process of fitting the theoretical curves to the experimental points constituted a determination of Young's modulus E for each rubber specimen. As a check on the experimental results, and also on the theory employed, determinations of E were also made by two additional methods, namely, from rough stess-strain curves, and from the relation E=3γρRT/Mc. With one exception, the internal agreement between the three determinations of E for the four different samples was satisfactory. The exception noted can probably be ascribed to the use of too small a value of Mc for the sample of lowest chain molecular weight.

Viscoelastic relaxation in poly-1-butenes of low molecular weight

1967 ◽  
Vol 300 (1462) ◽  
pp. 356-372 ◽  
Keyword(s):  
Molecular Weight ◽  
Steady Flow ◽  
Simple Liquid ◽  
Viscoelastic Relaxation ◽  
Low Frequencies ◽  
Chain Polymer ◽  
Molecular Weights ◽  
Wide Range ◽  
Volume Equation ◽  
Rouse Theory

Measurements have been made of the viscoelastic properties of a range of poly-1-butene liquids of different molecular weights under cyclic shearing stress. The five liquids studied range in steady-flow viscosity at 20 °C from 5.5 to 9330 P corresponding to number average molecular weights from 448 to 2700. Measurements over the temperature range – 60 to +90 °C were made at frequencies of alternating shear of 64 kc/s, 6, 18 and 30 Mc/s. The liquid of lowest molecular weight (448) was nominally pure, having eight repeat units, while the remaining four each had a distribution of molecular weights. In all cases, the dependence of steady flow viscosity upon temperature follows the equation In η = A + B /(T - T 0 ), (1) which is derived from the free-volume equation with a linear dependence of density upon temperature. Recent measurements on a wide range of pure liquids which have viscosities described by equation (1) have been interpreted in terms of a simple phenomenological model for viscoelastic relaxation which allows the behaviour to be predicted (Barlow, Erginsav & Lamb 1967 b ). Analysis of the present results on the liquid of lowest molecular weight shows that the measured behaviour can also be described by this model. For the four liquids of higher molecular weight a second relaxation process is found at lower frequencies. This is attributed to the increased chain length of the molecules giving rise to 'quasi-Rouse’ modes of motion. At low frequencies the results for these four liquids show a behaviour intermediate between that of a simple liquid and that exhibited by a long chain polymer which conforms to the extended form of the Rouse theory.

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.

Synthesis, Characterization, and Dynamics of a Rod/Sphere Organoceramic Composite Liquid

1992 ◽  
Vol 274 ◽  
Author(s):  
Mark A. Tracy ◽  
R. Pecora
Keyword(s):  
Experimental Studies ◽  
Liquid System ◽  
Organic Coating ◽  
Molecular Weights ◽  
Naturally Occurring ◽  
Wide Range ◽  
Molecular Composites ◽  
Ceramic Precursors ◽  
Rigid Rod ◽  
System 1

ABSTRACTComposite liquids – liquids composed of polymers, particles, and small molecule solvents – constitute an important class of synthetic and naturally occurring materials. Examples include molecular composites, ceramic precursors, lubricants, adhesives, and the cytoplasm in biological cells. Due to the complexity of these liquids, experimental studies of precisely defined systems are essential in developing an understanding of the interactions between all components in the liquid. Unfortunately, such fundamental studies have been relatively rare due to both the difficulty of synthesizing precisely defined composite liquids and the lack of adequate experimental methods to monitor the motions of the various constituents.We have recently reported the synthesis, characterization and some studies of the dynamics of a rod/sphere composite liquid system [1]. In our case the “polymer” constituent is a rigid rod polymer, poly(γ-benzyl-α,L-glutamate) (PBLG). Rigid rod polymers are frequently used in composite liquids as viscosity enhancers. PBLG is commercially available in a wide range of molecular weights and its static and dynamic behavior in dilute and nondilute solutions has been studied. It, in addition, forms mesophases in the concentrated regime. The ceramic “particles” in our composite liquid are coated silica spheres. These spheres are synthesized by the method of Stober et. al. [2] and coated with an organic coating (3-(trimethoxysilyl)propyl methacrylate (TPM)) following a procedure based on that of Philipse et. al. [3] to render them dispersible in organic solvents. The spheres with sizes in the range from 10 nm up to almost 1μm can be synthesized with a relatively narrow size distribution. The solvent in our studies is dimethylformamide (DMF). Both polymer and particle are dispersible as singlets (nonaggregating) in these solvents and the PBLG retains its rigid (or nearly rigid) rod conformation. The diffusion of both the polymer and the sphere in the composite liquid is measured by dynamic light scattering (DLS) [4]. In this paper, we focus on the spheres and examine the effects of rod concentration and rod length on the diffusion of different size spheres. This study suggests that the solution microstructure has an important influence on sphere diffusion.

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