Copolymerization of a Polydisperse Oligomer with a Monodisperse Chain Extender with Intramolecular Reaction Allowed

SARMORIA, C; VALLÉS, E M

MACROMOLECULES

American Chemical Society

Lugar: Washington DC; Año: 1995 vol. 28 p. 6244 - 6253

0024-9297

We have modeled stepwise, irreversible copolymerizations with intramolecular reaction allowed where one of the reactants is a polydisperse oligomer. A2 + B2 systems are studied, where A2 is the bifunctional chain extender and B2 is the bifunctional oligomer. Two models are presented. They are both extensions of a previous one where B2 was assumed to be monodisperse. In both cases B2 is approximated as the sum of N monodisperse fractions. In one model, it is necessary to write a system of kinetic equations to describe the A2 + (B2)l+ (B2)2 + ... + (B2)N copolymerization where all the B-fractions are simultaneously available for reaction. In the second model, N different monodisperse systems are set up and made to react separate and simultaneously. The species from these N systems are then combined using probability theory. This results in an important reduction in the number of equations needed. The theoretical error involved in this second model is small. Our results indicate that disregard for both polydispersity and ring formation may result in sizable errors in the prediction of average molecular weights.