Molecular Weight of GR-S Fractions. Simple Glass Osmometer for Use in Hydrocarbon Solvents

1947 ◽  
Vol 20 (4) ◽  
pp. 984-989
Author(s):  
David M. French ◽  
Roswell H. Ewart
Keyword(s):  
Molecular Weight ◽  
Molecular Weights ◽  
Hydrocarbon Solvents ◽  
The Relationship

Abstract Osmotic molecular weight measurements have been made on a sample of unfractionated GR-S and on eight fractions of this material. The molecular weights ranged from 10,000 to approximately 1,000,000, with a number average at 92,000. The relationship between molecular weight and viscosity for GR-S was determined. A simple all-glass osmometer for use in hydrocarbon solvents is described, and information on its use and the membranes employed is given.

scholarly journals Molecular Simulation of Hyperbranched Polyester

2009 ◽  
Vol 5 (1) ◽  
pp. 563-569
Author(s):  
Liu Yanmei ◽  
Li Haihua ◽  
Tai Yulei ◽  
Chao Guoku ◽  
Zhao Yajuan
Keyword(s):  
Molecular Weight ◽  
Simulation Model ◽  
Empirical Equation ◽  
Gel Permeation Chromatography ◽  
Acid Value ◽  
Hyperbranched Polyester ◽  
Molecular Weights ◽  
The Core ◽  
Relationship Of ◽  
The Relationship

A new types of hyperbranched polyester was synthesized by the 2,2-bis(hydroxymethyl) propionic acid as an AB2-type monomer and glycerol as the core moiety. Molecular weights were confirmed by Gel Permeation Chromatography. Acid values were titrated by KOH. The hydroxy value was obtained by titration. Furthermore, we calculate logarithmic value of acid value, hydroxy value, and molecular weight, respectively, and the simulation model curves were obtained. Based on the simulation model curves, we establish the empirical equation of the relationship of molecular weight, acid value and hydroxy value.

Physical Properties of Fractions of GR-S and Their Vulcanizates

1949 ◽  
Vol 22 (2) ◽  
pp. 494-517 ◽  
Author(s):  
John A. Yanko
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Large Scale ◽  
Average Molecular Weight ◽  
Three Dimensional ◽  
Reduced Pressure ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
Straight Line ◽  
The Relationship

Abstract A large-scale precise fractionation of GR-S (X-55) was carried out at 25° C, using a fractional precipitation technique. Nine fractions, each weighing approximately 150 grams and comprising about 11 per cent by weight of the original unfractionated sample, were obtained, with number-average molecular weights varying from 4000 to 1,650,000. High molecular fractions undergo gelation rapidly, even when dried in the absence of light at reduced pressure, and the higher the molecular weight of the fraction, the greater the amount of gel formed. Compared to unfractionated butadiene-styrene copolymers of similar gel contents, the gel portions of the higher molecular fractions had unusually high swelling indices, indicating qualitatively that the average molecular weights between points of effective cross-linking in the three-dimensional gel structure were higher than those found in the past in unfractionated samples of similar gel contents. Through the concentration range studied, the intrinsic viscosity values varied as a straight-line function of the concentration terms for all the fractions. However, the negative slopes of these lines increased as the molecular weight of the fraction increased, demonstrating the greater dependence of the intrinsic viscosity values of the higher molecular fractions on the concentration variable. The relationship between number-average molecular weight, as determined by osmometric measurements, and limiting intrinsic viscosity of the GR-S fractions is given by the equation: [η]0=5.4×10−4 M0.66, which is similar to that obtained by French and Ewart. The μi values calculated from the equation of Huggins were essentially the same (0.35) through the molecular range 12,400 to 723,000.

scholarly journals Intrinsic Viscosity-molecular Weight Relationship of Poly (Hexanediol Adipate)

2019 ◽  
pp. 1-8
Author(s):  
Jiankun Li ◽  
Zegang Zong ◽  
Dehua Hou ◽  
Bojun Tu ◽  
Weilan Xue ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Average Molecular Weight ◽  
Group Analysis ◽  
Gel Permeation Chromatography ◽  
Molecular Weights ◽  
The One ◽  
Relationship Of ◽  
The Relationship ◽  
End Group

In this work, a series of poly(Hexanediol adipate)(PHA) samples (103＜Mn＜104) with narrow molecular weight distribution were prepared by the polymerization between adilic acid and 1,6-hexandiol. End-group analysis was applied to determine the number average molecular weight (Mn) of PHA. Gel permeation chromatography (GPC) was employed to obtain the average molecular weights (Mn, Mv, Mw).The intrinsic viscosity of the samples in the tetrahydrofuran (THF) solution was determined at 298 K by the dilution extrapolation method and the one-point method. The relationship between the intrinsic viscosity and the molecular weight for PHA was studied by the Mark-Houwink-Sakurada (MHS) equation, and the parameters of equation were determined.

Effect of the molecular weight and its distribution of polyvinylidene fluoride on the relationship between the spinning process, microstructure and properties of hollow fiber membranes via thermally induced phase separation

2018 ◽  
Vol 89 (7) ◽  
pp. 1311-1320 ◽  
Author(s):  
Nana Li ◽  
Zhe Chang ◽  
Qingchen Lu ◽  
Changfa Xiao ◽  
Junyi Wu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Polyvinylidene Fluoride ◽  
Crystallization Behavior ◽  
Water Flux ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
Molecular Weights ◽  
Spinning Process ◽  
The Relationship

Polyvinylidene fluoride (PVDF) is an important material in the preparation of ultrafiltration membranes via the thermally induced phase separation (TIPS) method. In this paper, four PVDF hollow fiber membranes with different molecular weights were prepared via the TIPS method by using dibutyl phthalate and dioctyl phthalate as a mixed diluent. The relationship between the molecular weight of PVDF and its distribution, phase separation, crystallization behavior and spinning process has been systematically studied. The effects of three factors on the microstructure and properties of the PVDF membrane have been analyzed. The flow behaviors of the PVDF/diluent and PVDF melt were tested by a capillary rheometer and a melt flow rate instrument, respectively. A phase diagram of the membrane solution was determined by thermal polarizing microscope and differential scanning calorimetry. The crystallization behavior and angle of orientation of the membrane were tested by using a differential scanning calorimeter and a sound velocity orientation measurement instrument. The microstructures, such as the pore structure and crystalline grain structure, were observed by field emission scanning electron microscopy. Meanwhile, the properties of the membrane were examined from the view of water flux, porosity and tensile testing. The results showed that changes in the polymer molecular weights affected not only the dynamics but also the thermodynamics of phase separation in membrane formation. As the PVDF molecular weight increased, the phase separation region increased, but the membrane structure became denser. A wide molecular weight distribution easily produced large pores. Then, the water flux decreased first and then increased.

Recent Advances in Anionic Synthesis of Functionalized Elastomers Using Functionalized Alkyllithium Initiators

1996 ◽  
Vol 69 (3) ◽  
pp. 444-461 ◽  
Author(s):  
Roderic P. Quirk ◽  
Sung Hoon Jang ◽  
Jungahn Kim
Keyword(s):  
Molecular Weight ◽  
Molecular Weights ◽  
Hydrocarbon Solvents ◽  
Molecular Weight Distributions ◽  
Recent Advances ◽  
Anionic Synthesis ◽  
Weight Distributions ◽  
Technological Developments ◽  
Α Chain

Abstract The results described herein demonstrate the advantages of functionalized initiators with respect to the efficiency of α-chain-end functionalization and the ability to effect post-polymerization functionalization and linking reactions with the living ω-carbanionic chain ends. Not all functionalized initiators are useful, however, because either: (a) they are not soluble in hydrocarbon solvents; or (b) they are not reactive enough to initiate polymerization at rates which are competitive with propagation to prepare polymers with narrow molecular weight distributions and controlled molecular weights; or (c) they are either too difficult to prepare or too expensive to prepare to be readily available for commercial elastomer production. The advantages of using funcitonalized initiators, however, should encourage further scientific and technological developments in this area.

scholarly journals On the Relationship Between Molecular Mass and Anticoagulant Activity in a Low Molecular Weight Heparin (Enoxaparin)

1992 ◽  
Vol 67 (05) ◽  
pp. 556-562 ◽  
Author(s):  
Ana-Victoria Bendetowicz ◽  
Elisabeth Pacaud ◽  
Suzette Béguin ◽  
André Uzan ◽  
H Coenraad Hemker
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
Low Molecular Weight Heparin ◽  
Anticoagulant Activity ◽  
Low Molecular Weight ◽  
Gel Chromatography ◽  
Molecular Weights ◽  
Thrombin Inhibition ◽  
Specific Catalytic Activity ◽  
The Relationship

SummaryA low molecular weight heparin (enoxaparin, mean molecular weight ~ 4,400) was separated by gel chromatography into eight different fractions with a narrow distribution around the following mean molecular weights: 1,800, 2,400, 2,900, 4,200, 6,200, 8,600, 9,800 and 11,000. We compared the influence of enoxaparin on the generation of thrombin in plasma to that of the eight fractions.We determined: a) the % of material with high affinity to antithrombin III (HAM) and the % of HAM above the critical chainlength necessary to allow for thrombin inhibition (ACLM), b) the specific catalytic activity on the decay of endogenous thrombin, and c) the inhibition of over-all thrombin formation in the extrinsic and the intrinsic pathway. From b and c we calculated the inhibition of prothrombin conversion in these pathways.We found that a) there is a gradual decrease of the HAM fraction with decreasing molecular weight; b) the specific catalytic activity for the inactivation of thrombin does not vary significantly between the fractions when expressed in terms of ACLM; c) the potency to inhibit prothrombin conversion does not vary significantly between the fractions when expressed in terms of HAM.

scholarly journals Influence of hyaluronic acid transitions in tumor microenvironment on glioblastoma malignancy and invasive behavior

2018 ◽  
Author(s):  
Jee-Wei E Chen ◽  
Sara Pedron ◽  
Peter Shyu ◽  
Yuhang Hu ◽  
Jann N Sarkaria ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hyaluronic Acid ◽  
Cell Activity ◽  
Invasive Phenotype ◽  
Molecular Weights ◽  
New Information ◽  
Matrix Bound ◽  
The Relationship ◽  
Polymerization Conditions

AbstractThe extracellular matrix (ECM) is critical in tumor growth and invasive potential of cancer cells. In glioblastoma tumors, some components of the native brain ECM such as hyaluronic acid (HA) have been suggested as key regulators of processes associated with poor patient outlook such as invasion and therapeutic resistance. Given the importance of cell-mediated remodeling during invasion, it is likely that the molecular weight of available HA polymer may strongly influence GBM progression. Biomaterial platforms therefore provide a unique opportunity to systematically examine the influence of the molecular weight distribution of HA on GBM cell activity. Here we report the relationship between the molecular weight of matrix-bound HA within a methacrylamide-functionalized gelatin (GelMA) hydrogel, the invasive phenotype of a patient-derived xenograft GBM population that exhibits significant in vivo invasivity, and the local production of soluble HA during GBM cell invasion. Hyaluronic acid of different molecular weights spanning a range associated with cell-mediated remodeling (10, 60, and 500 kDa) was photopolymerized into GelMA hydrogels, with cell activity compared to GelMA only conditions (-HA). Polymerization conditions were tuned to create a homologous series of GelMA hydrogels with conserved poroelastic properties (i.e. shear modulus, Poisson’s ratio, and diffusivity). GBM migration was strongly influenced by HA molecular weight. While markers associated with active remodeling of the HA content, hyaluronan synthase and hyaluronidase, were found to be insensitive to matrix immobilized HA content. These results provide new information regarding the importance of local hyaluronic acid content on the invasive phenotype of GBM.

Long Chain Branching in Natural Hevea Rubber-Determination by Gel Permeation Chromatography

1981 ◽  
Vol 54 (1) ◽  
pp. 34-41 ◽  
Author(s):  
J. L. Angulo-Sanchez ◽  
P. Cabaulero-Mata
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Hydroxylamine Hydrochloride ◽  
Gel Permeation Chromatography ◽  
Branch Points ◽  
Long Chain Branching ◽  
Molecular Weights ◽  
Gel Permeation ◽  
The Relationship ◽  
Long Chain

Abstract The hevea brasiltensis rubber contains, besides the insoluble branched entities, linear and branched molecules in the soluble fraction. The branching characteristics found by analyzing fractions of different molecular weight of rubber coagulated from freshly tapped latex, stabilized with hydroxylamine hydrochloride are: (a) molecules with molecular weights above 6.5×104−1.0×105g/mol (depending on the branch points functionality) are branched and molecules below these limits are linear. (b) The relationship between number of branch points and the logarithm of molecular weight is linear. (c) The branching density is not independent of molecular weight, as has been assumed for several polymers, but it has a maximum. The maximum branching density found in the soluble fraction is between 10.2×10−6 and 31.6×10−6mol/g, which varies little with the molecular weight; it is possible that molecular species with higher values become insoluble. (d) Branching results ˜λ and gel content (36%) of the whole rubber gave a total of 93–98% of branched entities (sol and gel) and 2–7% of linear species.

scholarly journals Molecular weight dependent antistaphylococcal activities of oligomers/polymers synthesized from 3-aminopyridine

2010 ◽  
Vol 75 (9) ◽  
pp. 1203-1208 ◽  
Author(s):  
Cahit Akgul ◽  
Mehmet Yildirim
Keyword(s):  
Molecular Weight ◽  
Antibacterial Activities ◽  
Maximum Activity ◽  
Size Exclusion ◽  
Polycondensation Reaction ◽  
Reaction Conditions ◽  
Molecular Weights ◽  
Antistaphylococcal Activity ◽  
Exclusion Chromatography ◽  
The Relationship

The main aim of this study was to investigate the relationship between molecular weight and the antistaphylococcal activity of oligomers/polymers synthesized from 3-aminopyridine. Different oligomers/polymers were synthesized from 3-aminopyridine by changing the oxidative polycondensation reaction conditions. They were characterized by size exclusion chromatography and their antibacterial activities were compared by employing standardized susceptibility assays. The obtained experimental results demonstrated that 3-aminopyridine had no antistaphylococcal activity. However, as a result of polymerization, strong antistaphylococcal activity was obtained. Oligomers/polymers synthesized from 3-aminopyridine had varying degrees of antistaphylococcal activity and the maximum activity was obtained from relatively very short oligomers. It was therefore concluded that polymerization of 3-aminopyridine is required for antistaphylococcal activity and strength of this activity depends on the molecular weights of the synthesized molecules.

I - High Molecular Weight Urokinase (UK) and Different Molecular Weight Heparin (HP) Fractions in Fibrinolysis

1979 ◽  
Author(s):  
C. Villaverde ◽  
L. Badimón ◽  
F. Valdecasas
Keyword(s):  
Molecular Weight ◽  
Significant Inhibition ◽  
Chromogenic Substrate ◽  
Dosage Range ◽  
Molecular Weights ◽  
Fibrin Plate ◽  
The Uk ◽  
Relationship Of ◽  
The Relationship ◽  
Different Molecular Weight

Following our previous works on the interaction of UK and Hp (Thromb. Haem, 38, 105, 1977), we have carried out research to clarify the possible influence of the specific molecular weights characteristics in that interaction, We have studied the relationship of HMW-UK (54,000) to HMW and LMW Hp in rat blood. Inhibitors were evaluated by chromogenic substrate 5-2251 and by our method on an activated fibrin plate, and fibrinolysis by euglobulins. The HMW-UK was tested in a dosage range of 100 to 300 PI.U/ml and Hp ones were: from 0.001 to 1,000 I.U/ml. Hp did not alter the basal inhibitor levels measured on fibrin substrate but we obtained on synthetic substrate an inhibition of 12% on the basal value for all Hp dosages. HMW-Hp produced an increase in the fall of the inhibitory activity induced by HMW-UK for low dosages of Hp, whilst high dosages produced an increase of inhibition, suppressing the UK indeed reduction of inhibitor levels. For LMW-Hp the low dosages did not alter the UK effect while high ones imppreased it. Euglobulins activity HMW-UK induced were not modified by low dosages but high ones induced a highly significant inhibition (for both Hp fractions).

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