Reversible polycondensation characterized by unequal reactivities of functional groups

Abstract

Molecular weight distributions and moments for reversible condensation polymerizations with unequal reactivities of functional groups both in the forward and reverse steps, have been obtained. Results are qualitatively similar to those obtained for the corresponding irreversible case, i.e., MWD curves split into two, one for odd-n and one for even values of n for R (= reactivity of monomer with monomer/reactivity of other oligomers) larger than unity. When R is less than one, there is a preponderance of monomer in the reaction mass. However, these effects are considerable reduced due to the reversibility of polymerization. Comparison with Flory's most probable distribution indicates that this function represents the MWDs of the polymer for both irreversible and reversible cases only when the functional groups exhibit equal reactivity. For the unequal reactivity case, such a one-parameter (in terms of functional group conversion) characterization of the MWDs is unlikely.