Molecular Weight Distribution of Polymers from Rheological Measurements in Dilute Solution

1961 ◽  
Vol 35 (6) ◽  
pp. 2128-2132 ◽  
Author(s):  
Warner L. Peticolas
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Dilute Solution ◽  
Rheological Measurements

Molecular weight distribution from rheological measurements

1974 ◽  
Vol 13 (2) ◽  
pp. 278-282 ◽  
Author(s):  
G. Locati ◽  
L. Gargani ◽  
A. De Chirico
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Rheological Measurements

The Structure of Neoprene. I. The Molecular-Weight Distribution of Neoprene Type GN

1949 ◽  
Vol 22 (3) ◽  
pp. 680-689
Author(s):  
W. E. Mochel ◽  
J. B. Nichols ◽  
C. J. Mighton
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Osmotic Pressure ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Distribution Curve ◽  
Pressure Measurements ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Good Agreement

Abstract Polychloroprene rubber (Neoprene Type GN) was fractionated by partial precipitation from dilute solution in benzene and the fractions were examined both osmotically and viscometrically in benzene solutions. The molecular-weight distribution curve for Neoprene Type GN based on osmotic pressure measurements shows a pronounced maximum at 100,000, but has a long extension to molecular weights of over one million, indicating the presence of branched or cross-linked material which is still soluble. The uniformity is somewhat less than that of sol natural rubber, while in shape the Neoprene distribution curve resembles more closely that of peptized natural rubber than fresh sol rubber. Observed variations in the slopes of the π/c vs. c and the ηsp/c vs. c curves also indicate the presence in solution of complex, branched and (or) cross-linked molecules. Calibration of the intrinsic viscosity-molecular weight relationship by osmotic pressure measurements gave good agreement with the equation: [η]=KMa, where K=1.46×10−4 and a=0.73.

Evaluation of molecular weight distribution in linear polymers from rheological measurements

1972 ◽  
Vol 14 (10) ◽  
pp. 2653-2656 ◽  
Author(s):  
V.A. Grechanovskii ◽  
I.Ya. Poddubnyi ◽  
L.A. Nedoinova ◽  
Yu.G. Kamenev
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Linear Polymers ◽  
Rheological Measurements

Synthesis and Dilute-Solution Behavior of Model Star-Branched Polymers

1978 ◽  
Vol 51 (3) ◽  
pp. 406-436 ◽  
Author(s):  
B. J. Bauer ◽  
L. J. Fetters
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Melt Processing ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Dilute Solution ◽  
Long Chain

Abstract The occurrence of polymers branched in a random fashion is common. Chain transfer reactions can cause short- and long-chain branching in polymerizations such as the high-pressure polymerization of ethylene. Branching can also be introduced intentionally by the use of a polyfunctional monomer in end-linking polymerizations. Similar branching can be produced in addition polymerizations by the use of a small amount of difunctional monomer, e.g., divinylbenzene. There also has been much interest in graft polymerization by which long chain branches can be introduced onto a backbone, which is often a different polymer from the branches. The properties of branched polymers can be quite different from those of linear polymers of the same molecular weight. For example, bulk viscosities as well as concentrated and dilute solution viscosities can be lower for branched polymers than for a linear material of equivalent molecular weight. As an example, the melt processing behavior of polymers can be manipulated by alterations in the average molecular weight, molecular weight distribution, and the frequency and length of long branches in the molecules. Thus, there is an obvious need to correlate and characterize the type and degree of branching in a polymer with its effect on the physical properties in solution or melt. In all of the above examples of branching, there is a mixture of branched and unbranched material. The unbranched and branched polymers can have a wide molecular weight distribution, as can the branches themselves. Also, the frequency of branches and the segment lengths between branch points can vary. Hence, the physical properties of such materials represent an average of the properties of all the different species present.

scholarly journals Analytical Rheology of Polymer Melts: State of the Art

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Sachin Shanbhag
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Polymer Melts ◽  
State Of The Art ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Rheological Measurements ◽  
Unknown Sample ◽  
Extreme Sensitivity

The extreme sensitivity of rheology to the microstructure of polymer melts has prompted the development of “analytical rheology,” which seeks inferring the structure and composition of an unknown sample based on rheological measurements. Typically, this involves the inversion of a model, which may be mathematical, computational, or completely empirical. Despite the imperfect state of existing models, analytical rheology remains a practically useful enterprise. I review its successes and failures in inferring the molecular weight distribution of linear polymers and the branching content in branched polymers.

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