The solvation effect in the thermal decomposition of 2,2'-azoisobutyronitrile
in acrylonitrile/methyl methacrylate mixtures in diluted solutions of N,N-dimethylformamide
Polimery 2001, No 2, 125
The thermal decomposition rate constant (kd) of 2,2'-azoisobutyronitrile (AIBN) was studied in acrylonitrile (AN)-methyl methacrylate (MMA) comonomer mixtures dissolved in dilute solutions of N,N-dimethylformamide (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 = O, 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·• dm3. 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 forms occurring in the system AN-MMA/DMF/AIBN/ 60 °C, their relative stability constants and relative contents, and the thermal decomposition rate constants of the solvated forms were determined (Tables 2-5).
Keywords: radical copolymerization, thermal initiation, thermal decomposition of AIBN