spopmsThe study of chain-transfer reactions in thermal and AIBN-initiated polymerization of styrene is aimed a t the determination of transfer constants to the solvents at 60°C.For thermal polymerization the transfer constants Cs to acetone, chloroform, and chloroform mixed with acetone are 3.2 X 4.1 X 10-6, and 4.4 X 10-6, respectively. In the case of AIBN-initiated polymerization, the transfer constant of chloroform in the mixture acetone-chloroform is C . = 3.3 x lo-'. All these transfer constants are average values. It has been found that neither acetone nor chloroform satisfies the Mayo equation in the presence of transfer agent very well. These anomalies can be explained by assuming a complexation phenomenon. The changes in the polarity and resonance are taken into account. It is considered that in the chain-transfer reactions under investigation, the association or complex-forming ability of solvent and monomer or polymer play a role. In studying the chain-transfer reaction in the acetone-chloroform solvent mixture another phenomenon affecting the determination of the chain transfer constant is assumed. This phenomenon consists in formation of associates in which both solvents participate.
In this study some peculiarities in relation to the kinetics and especially the chain transfer reactions of the thermal polymerization of styrene in chloroform-acetone mixtures have been investigated. It has been found that the values of 1/P", the transfer constant for the solvent, kjk p2, and the fractional rate depend on the concentration of solvent. These anomalies are explained by the formation of complexes among the components of the polymerization system. Thereby the effect of the polarity of the medium must not be neglected.
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