Unsaturation of Polyisobutylenes and Butyl Rubber. Reactions with Nitrosobenzene, Thiocyanogen, Iodine Monochloride, and Ozone

1944 ◽  
Vol 17 (3) ◽  
pp. 679-692 ◽  
Author(s):  
John Rehner
Keyword(s):  
Molecular Weight ◽  
Small Molecules ◽  
Extreme Values ◽  
Average Molecular Weight ◽  
The Other ◽  
Iodine Monochloride ◽  
Incomplete Reaction ◽  
A Current ◽  
End Group ◽  
Good Agreement

Abstract Table III summarizes unsaturation values obtained for the various polymers. The ranges indicated are, in most cases, extreme values of determinations made with two or more different samples of a given polymer type. Taking into consideration the small amounts of unsaturation involved, the values based on end-group determinations are in reasonably good agreement with one another and with the values based on the viscosity of the degraded polymer. Higher values are observed for the nitrosobenzene determinations, but these are considered to be less reliable because of the ease with which oxidation phenomena can occur with this reagent. The thiocyanogen values are the lowest of all; on the basis of values obtained by the other methods as well as of experimental evidence not included in this paper, these values are believed to result from incomplete reaction. As a class the iodine monochloride methods give considerably higher values than those obtained with the other reagents. This may be attributed to the substitution reaction that readily occurs with that reagent. The effect is perhaps most marked in the data obtained for polyisobutylene sample 2 with 0.1 N Wijs reagent; the upper value (0.4) is far greater than can be explained on the basis of the knowa molecular weight of this polymer and the corresponding terminal double bond contribution. Furthermore, since this polymer sample was fractionated in such a way as to remove all species of viscosity-average molecular weight less than about 50,000, the high value cannot be ascribed to the presence of dimers, trimers, or other small molecules formed during polymerization. In view of the data and the above considerations, it is believed that the unsaturation values based on ozone degradation are correct within the limits of experimental error, and that this reagent makes possible a relatively good estimation of the number of double bonds in polymers such as have been described. A modified procedure more suitable for rapid evaluations is the object of a current investigation.

scholarly journals Self-Stable Precipitation Polymerization Molecular Entanglement Effect and Molecular Weight Simulations and Experiments

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2243
Author(s):  
Jiali Qu ◽  
Yi Gao ◽  
Wantai Yang
Keyword(s):  
Molecular Weight ◽  
Maleic Anhydride ◽  
Molecular Conformation ◽  
Average Molecular Weight ◽  
Precipitation Polymerization ◽  
Radius Of Gyration ◽  
Propagation Mechanism ◽  
Reactive Molecular Dynamics ◽  
End Distance ◽  
Good Agreement

In this paper, we developed a reactive molecular dynamics (RMD) scheme to simulate the Self-Stable Precipitation (SP) polymerization of 1-pentene and cyclopentene (C5) with maleic anhydride (MAn) in an all-atom resolution. We studied the chain propagation mechanism by tracking the changes in molecular conformation and analyzing end-to-end distance and radius of gyration. The results show that the main reason of chain termination in the reaction process was due to intramolecular cyclic entanglement, which made the active center wrapped in the center of the globular chain. After conducting the experiment in the same condition with the simulation, we found that the distribution trend and peak value of the molecular-weight-distribution curve in the simulation were consistent with experimental results. The simulated number average molecular weight (Mn) and weight average molecular weight (Mw) were in good agreement with the experiment. Moreover, the simulated molecular polydispersity index (PDI) for cyclopentene reaction with maleic anhydride was accurate, differing by 0.04 from the experimental value. These show that this model is suitable for C5–maleic anhydride self-stable precipitation polymerization and is expected to be used as a molecular weight prediction tool for other maleic anhydride self-stable precipitation polymerization system.

Continuous Ultrasonic Treatment of Uncured and Sulfur Cured SBR: Effect of Styrene Content

2005 ◽  
Vol 78 (4) ◽  
pp. 606-619 ◽  
Author(s):  
A. I. Isayev ◽  
S. H. Kim ◽  
Wenlai Feng
Keyword(s):  
Molecular Weight ◽  
Ultrasonic Treatment ◽  
Crosslink Density ◽  
Main Chain ◽  
Structural Characteristics ◽  
Average Molecular Weight ◽  
Chain Scission ◽  
Gel Fraction ◽  
Styrene Content ◽  
Good Agreement

Abstract Unvulcanized and vulcanized SBR samples with styrene content of 18 and 23.5% were used to investigate the effect of ultrasound treatment on their structural characteristics. Gel fraction and crosslink density of gel are measured. Molecular weight and molecular weight distribution of sol are studied to determine the level of degradation of the macromolecular chain in ultrasonically treated unvulcanized and vulcanized rubbers. It is shown that the weight and number average molecular weight of sol in devulcanized SBR is, respectively, lower and higher in the samples having higher styrene content. Ultrasonic treatment of virgin unvulcanized SBR causes generation of gel along with its main chain modification due to the competition between chain scission and crosslinking. The competitive reactions taking place during this treatment are discussed. It was found that the intermolecular bonds in SBR vulcanizates containing higher styrene content are easier to break. The structural characteristics of devulcanized SBR rubber were simulated using the Dobson-Gordon theory of rubber network statistics. A fairly good agreement between experimental data and theoretical prediction on normalized gel fraction vs. normalized crosslink density was achieved. The simulation of devulcanized SBR rubber indicated that the rate of crosslink rupture is much higher than that of main chain. The styrene content in SBR rubber does not affect kp/kα substantially.

End-Group Method for Molecular Weight Determination of PET Depolymerization under Microwave Irradiation

2012 ◽  
Vol 554-556 ◽  
pp. 1933-1937 ◽  
Author(s):  
Qing Hua Feng ◽  
Qing Hua Tang ◽  
Wei Lu Zhang ◽  
Yan Hua Jia ◽  
Dong Zhang
Keyword(s):  
Molecular Weight ◽  
Microwave Irradiation ◽  
Average Molecular Weight ◽  
Relative Number ◽  
Group Method ◽  
Molecular Weight Determination ◽  
Stannous Oxide ◽  
Hydrolytic Depolymerization ◽  
End Group

A series of catalysis hydrolytic depolymerization of PET catalyzed by zinc acetate, zinc sulfate, stannous oxide respectively under microwave irradiation at different temperature with time was studied, in which the microwave power was 260W, the ratio of water to PET was 10:1 and the dosage of the catalysts was 0.5% of PET. The relative number average molecular weight of the undepolymerized PET was determined by end-group method. The results show that the molecular weight of the undepolymerized PET decreases with the reaction time increasing, and tends to be stable at the end of the depolymerization reaction. Under the same time, the temperature is higher, the molecular weight is smaller. The molecular weight of the undepolymerized PET reduces most quickly with stannous oxide among the three catalysts.

Changes in the hemicellulosic polysaccharides of Avena coleoptile cell walls during growth of intact seedlings

1988 ◽  
Vol 66 (5) ◽  
pp. 949-954 ◽  
Author(s):  
M. Teresa Herrera ◽  
Ignacio Zarra
Keyword(s):  
Molecular Weight ◽  
Avena Sativa ◽  
Cell Walls ◽  
Average Molecular Weight ◽  
Relative Content ◽  
The Other ◽  
Polysaccharide Fraction ◽  
Avena Coleoptile ◽  
Main Component ◽  
Soluble Part

The variations taking place in the major polysaccharides of the cell wall of Avena sativa L. cv. Victory coleoptiles were studied during growth. Two fractions were obtained, one corresponding to cellulose and the other to the hemicelluloses. The relative content of cellulose was greater in the basal regions of the coleoptiles and the proportion of this polysaccharide fraction increased in all regions during growth. The hemicellulosic fraction was composed of two parts, an insoluble one designated the HC A hemicellulosic fraction, whose main component was seen to be an insoluble xyloglucan, and a soluble part designated the HC B hemicellulosic fraction, composed of an arabinoxylan and a (β1-3)- or (β1-4)-glucan. This latter was degraded during the growth of the coleoptiles. The average molecular weight of hemicelluloses HC A and HC B decreased from the sub-apical zones to the basal zones of the coleoptiles; this was related to the growth capacity of each of the regions into which the coleoptiles were divided.

First GPC results of terpyridine based chain extended supramolecular polymers: comparison with viscosity and analytical ultracentrifugation

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Michael A. R. Meier ◽  
Harald Hofmeier ◽  
Caroline H. Abeln ◽  
Christos Tziatzios ◽  
Mircea Rasa ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Analytical Ultracentrifugation ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Supramolecular Polymers ◽  
Supramolecular Polymer ◽  
Poly Ethylene ◽  
A Chain ◽  
First Time ◽  
Good Agreement

AbstractThe molecular weight of an extended metallo-supramolecular polymer, based on a α,ω-bis-terpyridine-poly(ethylene glycol) polymer linked via ruthenium(II) ions, was determined by gel permeation chromatography, viscosimetry as well as analytical ultracentrifugation. An optimized GPC method was applied for the first time to this kind of chain extended supramolecular polymers and the obtained results showed a good agreement with viscosimetry and analytical ultracentrifugation. A chain extended polymer with an average molecular weight of around 140 000 was found. These results clearly demonstrate that well-soluble high-molecular-weight metal-containing coordination polymers that are based on well-defined telechelics can be synthesized and fully characterized.

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.

THE FRACTIONATION OF POLYTHENE

1961 ◽  
Vol 39 (10) ◽  
pp. 1888-1891 ◽  
Author(s):  
W. R. Blackmore ◽  
W. Alexander
Keyword(s):  
Molecular Weight ◽  
Distribution Function ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Negative Binomial ◽  
Average Molecular Weight ◽  
Weight Average Molecular Weight ◽  
Log Normal ◽  
Molecular Weight Fractions ◽  
Good Agreement

An apparatus is described for fractionating large quantities (400 g) of polythene into five roughly equal fractions using a fractional precipitation technique. Application of this method of fractionation to a linear polythene has shown that the width of the molecular-weight distribution of the successive fractions decreases as the fractionation proceeds. Consequently, the initial high-molecular-weight fractions require refractionation to produce equally narrow distributions in them as are found in later fractions. Good agreement is obtained with the experimentally determined values of the number-average and weight-average molecular weight for the parent polymer when the measured values of Mn and Mw for each fraction are used to calculate the values for the parent. The differential molecular-weight distribution function of the parent polymer was calculated on a Bendix G-15 computer from the data for the fractions by using the weight, number-average and weight-average molecular weight, measured for each fraction in conjunction with an assumed log-normal or negative binomial molecular-weight distribution function in each fraction.

Apparent molal volumes and heat capacities of low molecular weight peptides in water at 25 °C

1978 ◽  
Vol 56 (21) ◽  
pp. 2707-2713 ◽  
Author(s):  
Carmel Jolicoeur ◽  
Jeannine Boileau
Keyword(s):  
Molecular Weight ◽  
Polypeptide Chain ◽  
Necessary Conditions ◽  
The Other ◽  
Low Molecular Weight ◽  
Flow Microcalorimetry ◽  
Apparent Molal Volumes ◽  
Amino Acid Side Chains ◽  
Molal Volumes ◽  
End Group

The apparent molal volumes [Formula: see text] and beat capacities [Formula: see text] of oligopeptides of glycine, alanine, and serine have been determined in water at 25 °C by flow densimetry and flow microcalorimetry. The data are reported for the homologous series: glycine to pentaglycine, L-alanine to tetra-L-alanine and L-serine to tri-L-serine. From the limiting [Formula: see text] and [Formula: see text] values of the glycine oligomers, the contributions of the glycyl residue in an extended polypeptide chain has been evaluated as: [Formula: see text] and [Formula: see text] The data for the other peptides are discussed in terms of contributions from the amino acid side chains, i.e. —CH3 and —CH2OH, and end-group hydration effects. Some necessary conditions for obtaining useful additivity schemes for predicting [Formula: see text] and [Formula: see text] of extended polypeptides and proteins are indicated.

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