Verification of the Flory Theory of Random Reorganization of Molecular Weight Distribution—Kinetics of Methylsiloxane Polymerization

1965 ◽  
Vol 69 (7) ◽  
pp. 2213-2217 ◽  
Author(s):  
Jack B. Carmichael ◽  
James Heffel
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Flory Theory ◽  
Distribution Kinetics ◽  
Kinetics Of

The kinetics of the polymerization of sarcosine carbonic anhydride

1949 ◽  
Vol 199 (1059) ◽  
pp. 499-517 ◽  
Keyword(s):  
Molecular Weight ◽  
Equilibrium Constant ◽  
Intrinsic Viscosity ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Intermediate Compound ◽  
Preparative Method ◽  
Kinetics Of

The polymerization of carbonic anhydrides, a reaction important but>u as a preparative method for the synthesis of polypeptides and as an example of a less familiar type of polymerization, has been studied in detail using sarcosine carbonic anhydride (I). The propagation reaction has been shown to involve a reversibly formed compound between the carbonic anhydride and the polymer; this compound decomposes by both a unimolecular and a bimolecular route. The equilibrium constant for the formation of the intermediate compound, and both velocity constants for its decomposition have been determined in two solvents, and the energies of activation and frequency factors calculated. The molecular weight distribution has been calculated; it is extremely sharp. The viscosities of the polymers prepared by this reaction have been measured, and the relation between the intrinsic viscosity and the molecular weight established.

Equilibrium Molecular Weight Distribution of Cyclic and Linear Methylsiloxanes

1967 ◽  
Vol 40 (4) ◽  
pp. 1084-1093 ◽  
Author(s):  
Jack B. Carmichael ◽  
James Heffel
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Equilibrium Constants ◽  
Molecular Size ◽  
Size Distributions ◽  
Flory Theory ◽  
Molecular Weights ◽  
Cyclic Molecules

Abstract Data are reported for the equilibrium molecular size distributions of cyclic and linear methylsiloxanes in five polymers with number average molecular weights ranging from 459 to 1348. The distributions of linear species agree with the earlier work of Scott and agree reasonably well with the Flory theory of random reorganization. The amounts of cyclic molecules are sharply dependent on molecular weight. However, the equilibrium constants for cyclic formation for cyclic species with four to eight units are shown to be virtually identical with the equilibrium constants for cyclic formation in high molecular weight polymers reported in a previous publication. For octamethylcyclotetrasiloxane, Kav in moles of siloxane units per liter was found to be 0.72 in this study. For high polymers, Kav was previously reported to be 0.74.

The Dispersion of Carbon Black in Rubber Part IV. The Kinetics of Carbon Black Dispersion in Various Polymers

1994 ◽  
Vol 67 (2) ◽  
pp. 237-251 ◽  
Author(s):  
A. Y. Coran ◽  
F. Ignatz-Hoover ◽  
P. C. Smakula
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Natural Rubber ◽  
Kinetic Parameters ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Rapid Technique ◽  
Rubber Part ◽  
Kinetics Of ◽  
Carbon Black Dispersion

Abstract A rapid technique for evaluating the rate and state of dispersion of carbon black in natural rubber has been extended to study the dispersion of carbon black in various polymers. The technique measures the extent and rate of dispersion of the black in the rubber. The kinetics of dispersion was characterized for a variety of polymers (e.g. SBR, EPDM, IR, IIR, BR and NR). Kinetic parameters were correlated with molecular weight and molecular weight distribution.

Verification of the Flory Theory of Random Reorganization of Molecular Weight Distribution. Kinetics of Methylsiloxane Polymerization

1967 ◽  
Vol 40 (3) ◽  
pp. 769-776 ◽  
Author(s):  
Jack B. Carmichael ◽  
James Heffel
Keyword(s):  
Molecular Weight ◽  
Liquid Chromatography ◽  
Molecular Size ◽  
Gas Liquid Chromatography ◽  
Flory Theory ◽  
Distribution Kinetics ◽  
Linear Chains ◽  
Reaction Proceeds ◽  
Catalyzed Reactions ◽  
Kinetics Of

Abstract Distributions of linear and cyclic methylsiloxanes were determined by gas liquid chromatography during acid clay catalyzed reactions of equal molar amounts of D4[D= (CH3)2SiO] and MM[M= (CH3)3SiO1/2 at 80° C. Theoretical and experimental distributions of the linear siloxanes are compared as a function of time. The relatively large amounts of MD4M and MD8M present after 0.5 h indicate that D4 initially enters the linear chains as a unit. Sufficient reorganization has occurred after 0.5 h that the distribution of MD10M through MD13M is approximately random. The distribution of shorter chains becomes increasingly random as the reaction proceeds toward equilibrium. A corollary to the above conclusions is that the rate constant for propagation of dimethylsiloxanes appears to be approximately independent of molecular size.

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