Oxygen-ascorbic acid-Copper(II) initiating system. A kinetic study of the polymerisation of methyl acrylate in aqueous medium

Abstract

Polymerisation of methyl acrylate (MA) initiated by O₂-ascorbic acid (AA)-Cu²⁺ system was studied in aqueous medium at 40°C. The rate of polymerisation R_p, was found to increase, remain constant, and then decrease with increasing [Cu²⁺]. R_p was found to depend on [Cu²⁺]^0,6, [AA]⁰, [O₂]^0,6, and [MA]^1,3 in the increasing region, on [Cu²⁺]⁰, [AA]⁰, [O₂]^0,6, and [MA]^1,6 in the constant region and on [Cu²⁺]^-0,9, [AA]⁰, [O₂]^0,7, and [MA]^2,0 in the decreasing region. Rate laws were derived assuming a plausible reaction mechanism for the different regions. R_p increased with ionic strength and decreased with [H₂SO_4,]. An initial increase, then steady state followed by a decrease in rate with temperature was noticed in the range 25-55°C. k_p/k_t^½ values were calculated and compared with literature values. Chain lengths were determined viscometrically.