Analysis of a styrene-divinylester copolymerization: reaction heats, double bond conversions and average sequence lengths

A simple model, based on the free radical copolymerization theory of Mayo a nd Lewis, is developed to predict reaction heats, calorimetric and molar co nversions and average sequence lengths, during the crosslinking reaction be tween a monounsaturated monomer (M-1) and a multiunsaturated comonomer (M-2 ) The M-2-double bonds are assumed to react independently with equal initia l reactivities. The input variables of the model are the initial reactivity ratios (r(10), r(20)) and their variation with the global molar conversion , the initial composition of the reactive mixture (f(10)) and the molar hea t of formation of the different bonds formed during the copolymerization (D elta H-11, Delta H-22, Delta H-12) The application of this model allows to calculate the overall molar and calorimetric double bond conversions (P-m a nd P-c), the heat developed during the reaction (Delta H-T), the conversion s corresponding to each type of unsaturations (P-c1, P-c2, P-m1, P-m2), and the average sequence lengths of the reacted bonds ([N-11] and [N-22]) Publ ished data of experimental comonomers conversions in the system styrene-div inylester (S-DVER) were satisfactorily reproduced by including a functional ity of both reactivity ratios with the overall conversion. Finally, it was shown that the assumption implicitly made in most published kinetic studies from the differential scanning calorimetric (DSC) data, that P-c and P-m a re equivalent, is not general and this feature must be investigated in orde r to perform correct kinetic calculations. (C) 2000 Elsevier Science Ltd. A ll rights reserved.