Calculation of molecular weight distribution of products of non-equilibrium polycondensation, considering the “substitution effect”

Development of a quantitative theory of polycondensation

“…A more detailed analytical and numerical results on the investigation of the irreversible homopolycondensation of monomer RA 2 was published in which the kinetic method was invoked to theoretically analyze MWD in the framework of the FSSE model [61]. This in-depth analysis provided an answer to the centrally important problem of the applicability of the statistical method for the calculation of the MWD of the polymer molecules in the system under examination.…”

“…For an ideal model, the foregoing stochastic process is a Markov chain with probability p of transition into the regular state. As applied to the FSSE model this stochastic process was rigorously proved [61] to be non Markovian since the probability of such a transition turns out to be predetermined by all preceding states. It is essential, however, that this dependence normally decays at scales n p several monomeric units long.…”

“…The main conclusions of the theoretical analysis of the FSSE model equations may be formulated as follows [61]. The distribution f W ðlÞ of the polymer length l within the oligomer region, for which l is less than n p ; may vary in appearance depending on the values of the kinetic parameters k ¼ k 1 =k 0 ; k 0 ¼ k 2 =k 0 ; and the conversion p: In particular, this distribution can be either bimodal or oscillatory.…”

“…More than a decade separates the publication [61] and papers by Irzhak et al [62,63], in which the same FSSE homopolycondensation model was addressed. They reformulated the calculation of the MWD in terms of small fragments of polymer molecules, called 'bond blocks'.…”

Gel Points in Selected Models of Network Polymerisation

“…The non-equivalence of statistical and kinetic models was pointed out for the first time by Kuchanov [17]. It is true of course that in random polymerisation both types of models describe the process in an identical manner, but after the introduction of different reactivities of the functional groups in the monomeric units (substitution effect) the situation changes.…”