Mechanochemical Transformation and Synthesis of Polymers

1961 ◽  
Vol 34 (1) ◽  
pp. 215-227 ◽  
Author(s):  
A. A. Berlin
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
High Speed ◽  
Rotation Speed ◽  
Mechanical Energy ◽  
Average Molecular Weight ◽  
Internal Stresses ◽  
Natural Polymers ◽  
Specific Viscosity ◽  
Mechanical Breakdown

Abstract The mechanical grinding, milling, mixing, homogenization, freezing and other processes of the physico-mechanical processing of high polymers are widely used in the industries of plastics, rubbers, synthetic fibers, food products, silicates and many other branches of technology. Some of these processes have a great significance in biochemistry, medicine and biology. An analysis of the available experimental data permits one to reach the conclusion that in the intensive grinding of natural polymers (cellulose, starch, proteins or synthetics (polystyrene, rubber, polyisobutylene, etc.) a mechanical scission (cracking) of the macromolecules is observed. The possibility of macromoleeular scission under the grinding of high molecular weight substances is due to the high probability of a localization of mechanical energy at different sections of the polymer chain, which under certain conditions causes internal stresses exceeding the strength of covalent or ionic bonds. Mechanical breakdown of macromolecules is possible not only with dry or wet grinding, but also by mechanical action on polymer solutions. Thus, for instance, Staudinger has shown that the high speeds and forces of friction developed in forcing a 0.005 molar tetralin solution of polystyrene, average molecular weight = Mave=6⋅106, through a platinum capillary bring about a scission of the macromolecules which is revealed in a decrease of about 30% in the specific viscosity of the solution. Forcing a solution of polyisobutylene (Mave=3.9×104–23×104) in dichlorobenzene through a capillary with a diameter of 0.2 mm causes a decrease in the intrinsic viscosity and an increase in the constant of the Huggins equation. An increase in the Mave of the polymer structure formation (cross-linking) and a repeated forcing through is conducive to the mechanical breakdown of the macromolecules. It has been established that in mixing together solutions of polymeric substances (starch, gelatine, polyvinyl alcohol, etc.) with high-speed mixers having a rotation speed of over 4000 rpm, a sharp decrease in the intrinsic viscosity [ν] is observed, while the degree of scission increases, with an increase in the rotation speed of the mixer, and also with a decrease in the concentration of the solution.

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.

scholarly journals Extraction, Characterization, and Molecular Weight Determination ofSenna tora(L.) Seed Polysaccharide

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Harshal A. Pawar ◽  
K. G. Lalitha
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Flow Property ◽  
Stability Study ◽  
Angle Of Repose ◽  
Molecular Weight Determination ◽  
Pharmaceutical Excipient ◽  
Accelerated Stability

The objective of the present work was extraction of polysaccharide fromSenna toraL. seed and its characterization as a pharmaceutical excipient. Polysaccharide extraction was based on mechanical separation of the endosperm of seeds ofSenna tora, water dissolution, centrifugation, and precipitation with acetone. Standard procedures were used to study the viscosity, micromeritic properties, and microbial bioburden. Accelerated stability study was carried out on isolated polysaccharide for six months at 40°C/75 RH as per ICH guidelines. The gum obtained fromS. toraseeds was an amorphous free flowing odourless powder with dull brown colour (yield = 35% w/w). The bulk density, tapped density, and angle of repose data reveal thatS. toragum possesses good flow property. The intrinsic viscosity obtained was 1.568 dL/g. The average molecular weight of purifiedS. toragum was found to be 198 kDa by intrinsic viscosity method. The results indicated that viscosity of gum solution increases with increase in temperature. FTIR study revealed the absence of degradation or decomposition of polysaccharide at accelerated stability conditions for six months. It has been concluded that extracted polysaccharide can be used as pharmaceutical excipient in terms of flow behavior, microbial properties, and stability.

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.

Physicochemical and chemical studies on wheat embryo ribosomal proteins

1968 ◽  
Vol 46 (4) ◽  
pp. 373-380 ◽  
Author(s):  
Fred H. Wolfe ◽  
Cyril M. Kay
Keyword(s):  
Molecular Weight ◽  
Ribosomal Proteins ◽  
High Speed ◽  
Polyacrylamide Gel Electrophoresis ◽  
Average Molecular Weight ◽  
Optical Rotatory Dispersion ◽  
Random Coil ◽  
Wheat Embryo ◽  
Molecular Weights ◽  
A Value

The physical heterogeneity of unfractionated wheat embryo ribsomal proteins, prepared by the glacial acetic acid method of Waller and Harris, has been investigated in 8 M urea −10−3 M dithio-threitol solutions of low pH (4.5). Sedimentation–diffusion measurements resulted in a weight average molecular weight of 29 000 ± 2 500, with no obvious evidence of heterogeneity. High-speed membrane osmometry was employed to establish the number average molecular weight of this system as 24 500 ± 1 000. The disparity in molecular weight averages suggests some size heterogeneity, and statistical analysis based on the two average molecular weights resulted in a calculated range of molecular weights for wheat embryo ribosomal proteins from 15 000 to 34 000 a.m.u. Charge differences, reflecting presumably primary structure differences, also exist among the members of this class, since about 26 different bands were resolved on polyacrylamide gel electrophoresis. The weight intrinsic viscosity of the ribosomal proteins in 8 M urea solutions was established as 0.273 dl/g, a value considerably larger than most globular proteins, suggesting that a major portion of their polypeptide chains are unfolded in this solvent. This conclusion was substantiated by optical rotatory dispersion measurements on this system, which resulted in a dispersion constant, λc, of 213 m μ, a value typical of that of the random coil. Amino acid and N-terminal analyses are also reported for this system, and comparisons of both chemical and physicochemical parameters are made with ribosomal proteins of other sources.

Basicity, Water Solubility and Intrinsic Viscosity of Carboxymethyl Chitosan as a Biofunctional Material

2012 ◽  
Vol 531 ◽  
pp. 507-510 ◽  
Author(s):  
Xiang Ping Kong ◽  
Juan Wang ◽  
Chun Jie Wang ◽  
Xia Wu
Keyword(s):  
Molecular Weight ◽  
Acetic Acid ◽  
Intrinsic Viscosity ◽  
Water Solubility ◽  
Average Molecular Weight ◽  
Carboxymethyl Chitosan ◽  
Molecular Weight Determination ◽  
Solution Ph ◽  
Alkaline Conditions

The basicity, water solubility, intrinsic viscosity and molecular weight of carboxymethyl chitosan (CM-chitosan) were investigated. The solution pH remained at about 9.2 at the concentration of higher than 2.0 g/L. The isoelectric point of CM-chitosan was about 4.5 of pH, and the solubility of CM-chitosan at the solution pH of 2.0 to 6.0 was lower than 5 g/L. The acetic acid could be replaced by hydrochloric acid as solvent for the viscosity-average molecular weight determination of chitosan. The intrinsic viscosity values of CM-chitosan have significant differences in acidic and alkaline conditions. The viscosity-average molecular weight of CM-chitosan was (3.8 ± 0.2) × 105, consistent with that of product chitosan of blank test.

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.

PEMBUATAN BIOFLOKULAN DARI PATI TALAS (COLOCASIA ESCULENTA L. SCHOOTT) DAN POLYACRILAMIDE DENGAN METODE PENCANGKOKAN (GRAFTING)

EKUILIBIUM ◽  
2015 ◽  
Vol 14 (2) ◽  
Author(s):  
Mujtahid Kaavessina
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Clean Water ◽  
Natural Polymers ◽  
Straight Chain ◽  
Polymer Backbone ◽  
Chain Polymer ◽  
Two Phases ◽  
Termination Time ◽  
Flocculation Process

<p>Abstract: Clean water is the basic needs. One of the way to get clean water is using<br />flocculation process. The flocculant copolymer is the combination of natural polymers and<br />synthetic polymers that is more effective than the straight-chain polymer flocculants. Starchgraft-polyacrylamide</p><p>(St-g-PAM) is the copolymer flocculant. This flocculant is synthesized by<br />the grafting to separate into two phases. The first stage is the synthesis of non-terminated<br />polyacrylamide (nt-PAM) and then the grafting of the non-terminated polyacrylamide (nt-PAM)on taro starch polymer backbone. This study aims to determine the effect of initiator<br />concentration ratio, the concentration of the terminator, and the termination time of %GE, %GY,<br />intrinsic viscosity and molecular weight. Polymerization was carried out in a glass reactor<br />equipped with a stirrer and isothermal conditions. The resulting products were analyzed by FTIR.</p><p>The analysis shows the existence bonds of starch and acrylamide, the presence of these<br />groups proves that St-g-PAM was formed. The increase in the initiator concentration leads to an<br />increase % GY, intrinsic viscosity and molecular weight but subsequently decreased. The<br />increase in the concentration of terminator and the length time of termination cause % GY,<br />intrinsic viscosity and molecular weight decreased. In this study, the concentration of acrylamide<br />is smaller than the concentration of starch, it makes not all of the starch backbone can join the<br />acrylamide chain so %GE can not be calculated. Thus it can not explain the effect of the initiator<br />concentration, the concentration of the terminator, and the termination time of %GE<br />Keywords: Starch-graft-Polyacrylamide, grafting to, bioflocculant</p>

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