A Monte Carlo method was used to take thorough account of the influences of different reactivity ratios and initial feed compositions on copolymer microstructure. The model proves the lack of azeotropic behavior in systems in which rA 1 and rB 1 or vice versa; it is also able to calculate the drift in the copolymer properties: copolymer composition

and randomness parameter. Moreover

for each reactivity ratio pair given

there is a unique reaction conversion

at which macromolecules produced inherit their maximum allowed alterations. This critical conversion declines as initial feed composition increases. However

for systems with rA 1 and rB 1

as well as those with rA 1 and rB 1

the azeotropic behavior of the reactions is clearly observed. Besides

copolymer composition reaches azeotrope point at the end of the reaction when rA 1 and rB 1. Finally

for systems in which rA 1 and rB 1

randomness parameter becomes maximum at azeotrope point when rA equals rB.