The solvation effect in the thermal decomposition of 2,2'azoisobutyronitrile in acrylonitrile/methyl methacrylate mixtures in diluted solutios of N,N-dimethylformamide

摘要

The thermal decomposition rate constant (kd) of 2,2'-azoisobu- tyronitrile (AIBN) was studied in acrylonitrile (AN)-methyl methacrylate (MMA) comonomer mixtures dissolved in dilute solutions of N,N-dimethyl- formamide (DMF) as a function of the comonomer mixture composition and concentration in the solvent at 60°C. The relationships kd = f(XA' C) (xA - mole fraction of acrylonitrile in comonomer mixture, C -comonomer mixture concentration) produce convex curves in relation to the straight line drawn through the kd values obtained at the boundary conditions (xA = 0, xA = 1). The radius of curvature is related to concentration C, which was fixed at 0.1, 0.5, 1.0 and 3.0 mol. dm-3. The higher the dilution of the monomer mixture, the smaller the convexity of the kd = f(XA) curve. All the experimental courses of kd = f(XA) may be interpreted in terms of solvation of the initiator by monomer A (AN), monomer B (MMA) and solvent S (DMF). The solvation foi1J1s occurring in the system AN-MMAjDMF j AIBN j 60°C, their relative stability constants and relative contents, and the thermal decomposition rate constants of the solvated forms were determined (Tables 2-5).