Rate coefficients as a function of time during the afer-effect of a photoinduced crosslinking polymerization

摘要

The polymerization of a dimethacrylate monomer occurring in the dark after the initiating light has been switched off(so-called after-effect) was modeled by assuming of two different termination mechanisms:mono-molecular 9Model 1) and bimolecular (model 2).Time dependent mono-molecular termination(k_t~m) and bimolecular termination (k_t~b) rate coefficients and a time independent propagation rate coefficient k_p are used in the models.Both k_t~m and k_t~b are polynomial functions of time.A very important feature of the newly developed models is the free terms of polynomials correspond to values of k_t~m (Model 1) or k_p[P~·]0 (Model 2 ) at the moment of stopping the irradiation (t_dark=0;[P~·] 0 constitute macroradical concentrations at t_(dark=0).Those values can be considered as describing the process during continuous irradiation.Calculations were performed for eight photoinduced polymerization processes,in which initiation had been interrupted at various degrees of double bond conversions (denoted as starting conversions).It was found that the conversion dependence of k_t~b[P~·]0 and K_t~m parameters extrapolated to t_(dark)=0 appearing in two various termination models was similar.