Effects of complexing agents in radical copolymerization

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Abstract
Radical copolymerization of methyl methacrylate (MMA, M1) with various monomers has been studied in presence of modifiers, i.e., complexing agents (CA): ZnCl2, AlCl3, AlBr3, Al(C2H5)2Cl, forming coordinate complexes with ester group of the monomer and of the propagating radical. The comonomers of the first group form complexes of similar structure and stability as MMA, methyl acrylate, or butyl acrylate. The comonomers of the second group do not form complexes with the modifiers (vinylidene chloride, 2,6‐dichlorostyrene, p‐chlorostyrene, styrene). For all systems studied the copolymer composition follows the Mayo‐Lewis equation. In the first group of the systems the effective reactivity ratios (r1, r2) approach unity with increase of the CA molar content (r1 = r2 ≃ 1 at [(CA)/MMA] + [MA] ≥ 0,3) In the second group of the systems the values of r1 either increase to a limit value (at [CA]/[MMA] ≥ 0.3), pass through maximum, or decrease to a limiting value with the CA molar content. The values of r2 decrease in all systems. The character of variation of r1 and r2 has been explained in terms of effects of the CA's on reactivity of MMA and PMMA radical. The equations for the copolymer compositions in these systems have been derived.

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