Thermal decomposition of 2,2'-azobis (2-methyl-4-hydroxybutyl) propionate in the N,N-dimethylformamide/methyl methacrylate system

摘要

The thermal deocmposition of the initiator 2,2'-azobis (2-methyl-4-hydroxybutyl) propionate (AIB-BD) at 333 K in N,N-dimethylformamide (DMF), methyl methacryalte (MMA) and various DMF/MMA mixtures was studied by volumetric method. The values of the stationary rate AIB-BD of decomposition for various initial concentrations of the initiator [I]_0 (within the range of 0.067-0.132 mol ·d~(-3)) were determined according to differential eq. (7). These values, according to eq. (8), allowed to determinate the order(x) of initiator decomposition reaction [defined in eqs. (2) and (4)]. The order x can be regarded as equal to 1 for the whole system, i.e., from a pure solvent (DMF) to pure monomer (MMA). The presented method of determination of the ordex x cannot be replaced by the estimation of linearity of eq. (10) what is frequenlty used in the publications, since the other kinetic dpenedneces are also linear for X =1 and X = 2. The thermal decomposition rate constant (kd) of AIB-BD is equal 5.19 ·10~(-4)min~(-1) and 4.12·10~(-4)min~(-1) in pure DMF and MMA, respectively. The kd values concerning DMF/MMA mixtures were found to be dependent on the mixture composition. This depnedence is represented by a monotonically decreasing function of the monomer mole fraction (xM). The relation kd = f(xM) has been interpreted on the basis of model of initiator solvation by monomer MMA and solvent DMF [eqs. (11) and (12)]. The results obtained for the DMF/MMA/AIB-BD system were compared with (previously studied) DMF/MMA/AIBN system.