scholarly journals Gel Formation in Reversibly Cross-Linking Polymers

2021 ◽  
Author(s):  
Maud Formanek ◽  
Lorenzo Rovigatti ◽  
Emanuela Zaccarelli ◽  
Francesco Sciortino ◽  
Angel J. Moreno
Keyword(s):  
Cross Linking ◽  
Gel Formation

Gel formation and molecular weight distribution in long-chain polymers

1954 ◽  
Vol 222 (1151) ◽  
pp. 542-557 ◽  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Cross Linking ◽  
Average Weight ◽  
Gel Formation ◽  
Theoretical Derivation ◽  
Experimental Values ◽  
Long Chain

In long-chain polymers an insoluble network or gel may be produced when a number of the separate molecules are linked together. A theoretical derivation is given of the relationship between the amount of gel formed and the degree of cross-linking, in terms of the initial molecular weight distribution. It is shown that whatever the initial molecular weight distribution, incipient gelling occurs when there is on the average one cross-linked monomer per weight average molecule. The shape of the gel-cross-linking curve depends on the ratio of z average, z +1, . . . average molecular weight to the weight average. From experimental values of the curve it becomes possible to determine many of the constants of the molecular weight distribution in the original polymer. Expressions are derived for the number average, weight average and z average of the polymer as a function of cross-linking prior to gel formation, as well as the number and weight averages of the sol fraction after gelation. The average molecular weight between cross-links in the gel is calculated. A number of other functions of the sol and gel fractions are also given.

Effects of Cross-Linking and Branching on the Molecular Constitution of Diene Polymers

1948 ◽  
Vol 21 (2) ◽  
pp. 461-470
Author(s):  
Paul J. Flory
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Reaction Mechanisms ◽  
Structural Unit ◽  
Random Distribution ◽  
Average Chain Length ◽  
Cross Linking ◽  
Gel Formation ◽  
Molecular Constitution ◽  
Kinetic Treatment

Abstract Reaction mechanisms whereby cross-linked and branched polymer structures may be formed during the polymerization of dienes are discussed. A kinetic treatment of the formation of cross-linkages via the occasional addition of a free radical to the unsaturated carbon of a structural unit of a previously polymerized molecule is presented. It is pointed out that the rate of this addition step relative to monomer addition can be deduced from the average chain length and the conversion at which gelation occurs. Cross-linkages introduced by the mechanism under consideration are not distributed at random, but the deviations from a random distribution are unimportant except at high conversions. Conditions are examined under which the cross-linking reaction decreases the total number of molecules more rapidly than they are formed. Physical properties of polymers (with particular emphasis on vulcanized rubbers) are most conveniently interpreted in terms of (1) the primary molecular weight (i.e., molecular weight in the absence of cross-linkages) and its distribution, and (2) the concentration of cross-linkages. The actual molecular-weight distribution, which may be severely distorted by the presence of cross-linkages, is inappropriate for direct correlation with the more important physical properties. The modifiers or regulators commonly employed in diene polymerizations suppress gel formation by reducing the primary molecular weight; they do not actually reduce cross-linking. This reduction in molecular weight is not without other undesired consequences, however.

scholarly journals Selective Enzymatic Release and Gel Formation by Cross-Linking of Feruloylated Glucurono-Arabinoxylan from Corn Bran

2020 ◽  
Vol 8 (22) ◽  
pp. 8164-8174 ◽  
Author(s):  
Line Munk ◽  
Jan Muschiol ◽  
Kai Li ◽  
Ming Liu ◽  
Alixander Perzon ◽  
...  
Keyword(s):  
Cross Linking ◽  
Gel Formation ◽  
Corn Bran

Gel Formation via Physical Cross-Linking in the Soluble Conjugated Polymer, Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], in Solution by Addition of Alkanes

2008 ◽  
Vol 41 (17) ◽  
pp. 6500-6504 ◽  
Author(s):  
Po-Shen Wang ◽  
Hsin-Hung Lu ◽  
Ching-Yang Liu ◽  
Show-An Chen
Keyword(s):  
Conjugated Polymer ◽  
Cross Linking ◽  
Gel Formation

Cross-linking and gel formation in the thermal degradation of PVC

1976 ◽  
Vol 5 (3) ◽  
pp. 309-315 ◽  
Author(s):  
T. T. Nagy ◽  
B. Turcsányi ◽  
T. Kelen ◽  
F. Tüdős
Keyword(s):  
Thermal Degradation ◽  
Cross Linking ◽  
Gel Formation
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