Retardation of polymerization

EiNHORN, I. N., Chapter entitled Eire Retardance of Polymeric Materials in Reviews in Polymer Technology Vol. 1 (Ed. skeist, ].), Dekker, New York (1972)... 

J.W. Wheeler, Y. Zhang and J.C. Tebby, Proceedings 6th European Meeting on Fire Retardancy of Polymeric Materials, Lille (1997), pp. 90-1. 

A.F. Grand and C.A. Wilkie (eds), Fire Retardancy of Polymeric Materials, M. Dekker, New York, NY... 

Kuryla, W. C., and Papa, A. J Flame Retardancy of Polymeric Materials. 

Anomolous results have been observed in some emulsion polymerizations—inverse dependencies of N, Rp, and Xn on surfactant concentration. Some surfactants act as inhibitors or retarders of polymerization, especially of the more highly reactive radicals from vinyl acetate and vinyl chloride [Okamura and Motoyama, 1962 Stryker et al., 1967]. This is most apparent with surfactants possessing unsaturation (e.g., certain fatty acid soaps). Degradative chain transfer through allyl hydrogens is probably quite extensive. 

A termination frequently encountered in many polymerizations results from a chain transfer process. In a radical polymerization such a reaction involves usually a transfer of a hydrogen atom and yields a radical which may or may not initiate further polymerization. The first alternative may be referred to as a proper chain transfer reaction, and such a transferring agent is known as a polymerization modifier. The second alternative is known as an inhibition or retardation of polymerization, the inhibitor or retarder being a substance which forms a stable radical, not sufficiently reactive in respect to the monomer, and therefore unable to initiate further polymerization. 

Strong assodation between the growing end and the existance of solvation shell prevent the monomer from reaching the reaction center and this inhibits the polymerization. This effect accounts for the retardation of polymerization by Lewis acids. On the other hand, agents solvating the positive counter-ions tend to separate them from the growing ends and thus they enhance the polymerization. This may be the explanation for the observed catalytic influence of Lewis bases. 

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