Kinetics of Addition Polymerizations

Most addition polymerizations involve vinyl or diene monomers. The opening of a double bond can be catalyzed in several ways. Free-radical polymerization is the most common method for styrenic monomers, whereas coordination metal catalysis (Zigler-Natta and metallocene catalysis) is important for olefin polymerizations. The specitic reaction mechanism may generate some catalyst residues, but there are no true coproducts. There are no stoichiometry requirements, and equilibrium limitations are usually unimportant so that quite long chains are formed 7iv 500 is typical of addition polymers. 

The first step in an addition polymerization is initiation to form a polymer chain of length 1  

The moiety denoted as I is the initiator group. It can be as simple as a free radical or as complicated as a transition metal atom bonded to organic ligands and located on a catalytic support. The next step in the polymerization is propagation, that is, the repeated insertion of monomer units into the chain to create an incrementally longer chain  

The propagation reaction is a more mechanistic version of Equation 13.1 and accounts for most of the monomer consumption. The growth of the chain can be stopped by 

P is a finished polymer molecule and IPi starts a new chain. Growth is also stopped by termination. It deactivates the initiator group and gives a finished polymer molecule. 

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The kinetics of template polymerization depends, in the first place, on the type of polyreaction involved in polymer formation. The polycondensation process description is based on the Flory s assumptions which lead to a simple (in most cases of the second order), classic equation. The kinetics of addition polymerization is based on a well known scheme, in which classical rate equations are applied to the elementary processes (initiation, propagation, and termination), according to the general concept of chain reactions. 

Kinetics of Addition Polymerization. As the name suggests, addition polymerizations proceed by the addition of many monomer units to a single active center on the growing polymer chain. Though there are many types of active centers, and thus many types of addition polymerizations, such as anionic, cationic, and coordination polymerizations, the most common active center is a radical, usually formed at... 

Kucera M (1992) Mechanism and kinetics of addition polymerizations. Academia Press, Prague... 

New Techniques for the Study of Electrodes and their Reactions Electron Tunneling in Chemistry. Chemical Reactions over Large Distances Mechanism and Kinetics of Addition Polymerizations... 

M. KuCera, Mechanism and kinetics of addition polymerizations, in Comprehensive chemical kinetics, Vol. 31, H. G. Compton, ed., Elsevier, Amsterdam, 1992, ISBN 0444987959, Chapter 3, Section 1.3. 

Fink G, Miilhaupt R, Brintzinger HH, eds. Ziegler Catalysts. Berlin Springer-Verlag, 1995. Kucera M. Mechanism and Kinetics of Addition Polymerizations. Amsterdam Elsevier, 1992. Carraher CE, Moore JA. Modification of Polymers. New York Plenum Press, 1983. 

Kucera, M. Mechanism and Kinetics of Addition Polymerization-, Academia Prague Elsevier Science Amsterdam, 1992. 

The kinetics of addition polymerization contrast greatly with those for step-growth reactions since three distinct steps are involved. The initiation reaction takes place in two stages. First of all, the initiator molecules break down to form free radicals and then the radicals react with monomer molecules to form active centres. These two reactions have their own rate constants. 

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