Condensation polymerization kinetics

The kinetics of this type of polymerization are the same as for simple condensation for this reason, the use of the term polycondensation is perhaps more appropriate. Unless kinetic evidence suggests otherwise, polymerizations involving the formation of chain polymers from cyclic compounds, following ring scission, are classed as condensation polymerizations. Some important con-... 

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... 

A generalized kinetic treatment of the array of processes occurring in condensation polymerization might appear hopelessly complex. In the polyesterification of a hydroxy acid, for example, the first step is intermolecular esterification between two monomers, with the production of a dimer... 

The free amino group of the amino ester may then react analogously with another molecule of the monomer, etc. The kinetics of the polymerization are in harmony with a mechanism of this sort. The final polypeptide may contain up to 300 or more structural units. While the polymerization of N-carboxyanhydrides is closely analogous to the addition polymerizations of ethylene oxide and of other cyclic substances, definition unfortunately classifies it as a condensation polymerization inasmuch as carbon dioxide is eliminated in the process. 

Satisfactory kinetic data on condensation polymerizations other than... 

The combined results of kinetic studies on condensation polymerization reactions and on the degradation of various polymers by reactions which bring about chain scission demonstrate quite clearly that the chemical reactivity of a functional group does not ordinarily depend on the size of the molecule to which it is attached. Exceptions occur only when the chain is so short as to allow the specific effect of one end group on the reactivity of the other to be appreciable. Evidence from a third type of polymer reaction, namely, that in which the lateral substituents of the polymer chain undergo reaction without alteration in the degree of polymerization, also support this conclusion. The velocity of saponification of polyvinyl acetate, for example, is very nearly the same as that for ethyl acetate under the same conditions. ... 

Referring to the ADMET mechanism discussed previously in this chapter, it is evident that both intramolecular complexation as well as intermolecular re-bond formation can occur with respect to the metal carbene present on the monomer unit. If intramolecular complexation is favored, then a chelated complex, 12, can be formed that serves as a thermodynamic well in this reaction process. If this complex is sufficiently stable, then no further reaction occurs, and ADMET polymer condensation chemistry is obviated. If in fact the chelate complex is present in equilibrium with re complexation leading to a polycondensation route, then the net result is a reduction in the rate of polymerization as will be discussed later in this chapter. Finally, if 12 is not kinetically favored because of the distant nature of the metathesizing olefin bond, then its effect is minimal, and condensation polymerization proceeds efficiently. Keeping this in perspective, it becomes evident that a wide variety of functionalized polyolefins can be synthesized by using controlled monomer design, some of which are illustrated in Fig. 2. 

When a cychc monomer such a tetrahydrofuran or caprolactam is used as the monomer, the polymerization can be made to occur primarily by monomer reacting with the polymer rather than aU polymers reacting with each other. These kinetics are more tike addition polymerization, where only the monomer can react with the polymer. However, we stiU call this condensation polymerization because it produces this type of polymer. 

This volume contains 18 papers on the kinetics and technology of addition and condensation polymerization processes. These papers were presented at the sixth symposium on this subject held by the Division of Industrial and Engineering Chemistry and the Division of Polymer Chemistry during the A.C.S. Meeting, Boston April 9-14, 1972. They are concerned with known commercial products. New polymers and novel polymerization reactions presented at the same symposium are collected in the companion volume, Advances in Chemistry Series No. 129. 

Although Diels-Alder polymerizations involve a reaction of an unsaturated molecule, and the polymer does not have a structure typical of a condensation polymer, the characteristics of the polymerization reaction are those of a condensation polymerization. The kinetics of a Diels-Alder polymerization should be those of a typical condensation polymerization and involve a series of individual reactions, and not a chain type mechanism. A typical second-order rate expression, -dC/dt = kC2 should hold for a good portion of the polymerization reaction, where C is the concentration of both diene and dienophile ends. Typically, this rate would break down only when the molecular mobility is extremely low or when shielding of functional groups occurs in dilute solutions. 

The first 26 chapters of this volume are devoted to process improvements and the kinetics of addition and condensation polymerization of common monomers. The remaining 22 chapters are concerned with new and better polymers designed for a specific end use or physical property. 

Process Technology. In commercial addition and condensation polymerization processes reactor design is an important factor for the quality and economics of the polymer. Combining macromolecular kinetics with reactor and process design has led to a new concept called reaction engineering. D. C. Chappelear and R. H. M. Simon review this novel concept in Chapter 1. 

Macromolecules are formed by polycondensation and polymerization. Both reactions have been and are precisely defined and differentiated. For formal reasons, the term polymerization is superior to polycondensation (both lead to the formation of polymers) and polycondensation is then designated by the compromise term condensation polymerization+. In my opinion, due to the differences in the mechanism and kinetics of polymerizations and polycondensations, a separate treatment of each of these polyreactions is justified. 

Falling off of the log viscosity-time cure curve can also occur due to dewetting, or wall slip, at the cone-sample interface. This occurs rarely, in our experience, and probably more with highly filled samples as gelation is approached. A kinetic order greater than unity could also produce a curvature similar to C, but evidence of such kinetic orders for condensation polymerization reactions has not been reported from chemorheological studies, to our knowledge. (Certain types of addition polymerization reactions may show non-first-order viscosity kinetics.)(13)... 

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