Copolymerization of Partly Incompatible Monomers: An Insight from Computer Simulations
journal contributionposted on 14.06.2017, 15:20 by Alexey A. Gavrilov, Alexander V. Chertovich
We used dissipative particle dynamics simulations to study the copolymerization process in the presence of spatial heterogeneities caused by incompatibility between polymerizing monomers. We performed the model verification with the available literature data on styrene–acrylic acid copolymerization in the bulk, and a very good agreement between experimental and simulated data for both chain average composition and triad fractions was observed. Next, we studied the system properties for five model AB reaction processes with different sets of reactivity ratios at different compositions and Flory–Huggins parameters χ. We found that the system average copolymer composition does not change upon increasing χ value if the monomers have equal reactivity ratios rA = rB but changes toward higher A-monomer content if rA > rB. The local monomer fraction around growing chain ends was studied, and evidence of the presence of the bootstrap effect was found at nonzero values of χ. Next, significant changes in the copolymer sequences caused by the partial monomer incompatibility were observed: for all studied sets of reactivity ratios the resulting sequences demonstrated increased blockiness compared to the case of zero χ. Finally, we found that the reaction process in the presence of the monomer incompatibility cannot be described by a single set of terminal unit model reactivity ratios, as the “observable” reactivity ratios r′ extracted from the chain sequences depend strongly on the monomer feed composition.