THE MECHANISM OF THE COPOLYMERIZATION OF BF_3-COMPLEXED ETHYL ACRYLATE WITH PROPYLENE

The copolymerization of BF_2-omplexed ethyl acrylate with propylene in the presence ofAIBN at 25℃was investigated. It was found that the rate of the copolymerization was propor-tional to the square root of the initiator concentration. The chain transfer agent CCl_4 greatly af-fects the inherent viscosity of the resulting copolymer. The smaller the dielectric constant of thesolvent, the greater the rate of copolymerization is. The equal concentration of the two monomersgive the maximum copolymerization rate. The ~1H-NMR and ~(13)C-NMR analysis indicated, whenEA.BF_2]/EA.BF_2]+P]>0.5, the resulting copolymer was the acrylate-rich random copoly-mer. Through the kinetic experiments we suggest that copolymerization follows the mechanismof the random copolymerization of the ternary complex with binary complex. When EA.BF_3]/EA.BF_2]+P]<0.5, the resulting copolymer is always strictly alternating, and the alternatingcopolymerization follows the mechanism of the ternary complex homopolymerization. Usingthe homolog of the propylene, 1-pentene, we found that BF_3-complexed ethyl acrylate can forma ternary complex with 1-pentene identified by UV spectroscopy. This is a strong evidence forthe mechanism of ternary complex homopolymerizetion.

THE MECHANISM OF THE COPOLYMERIZATION OF BF3-COMPLEXED ETHYL ACRYLATE WITH PROPYLENE*

 The copolymerization of BF₂-omplexed ethyl acrylate with propylene in the presence ofAIBN at 25℃ was investigated. It was found that the rate of the copolymerization was propor-tional to the square root of the initiator concentration. The chain transfer agent CCl₄ greatly af-fects the inherent viscosity of the resulting copolymer. The smaller the dielectric constant of thesolvent, the greater the rate of copolymerization is. The equal concentration of the two monomers give the maximum copolymerization rate.The ^{1<,/sup>H-NMR and 13C-NMR analysis indicated,when EA·BF₃]/EA·BF₂]+P]>0.5,the resulting copolymer was the acrylate-rich random copolymer.Through the linetic experiments we suggest that copolymerization follows the mechanism of the random copolymerization of the ternary complex with binary complex.When EA·BF₃]/EA·BF₃]+P]≤0.5,the resulting copolymer is always strictly alternatin,and the alternating copolymerization follows the mechanism of the ternary complex homopolymerization.Using the homolog of the proptlene,1-pentene,we found that BF₂-complexed ethyl carylate can form a ternary complex with 1-pentene identified by UV spectroscopy.This is a strong evidence for the mechanism of ternary complex homopolymerization.}