title: Assessment of a Cost-Effective Approach to the Calculation of Kinetic and Thermodynamic Properties of Methyl Methacrylate Homopolymerization: A Comprehensive Theoretical Study.
abstract: In this work, we carried out a comprehensive density functional theory (DFT) study on the basis of a trimer-to-tetramer radical reaction model to assess a cost-effective approach to perform the calculation of kinetic and thermodynamic properties of methyl methacrylate (MMA) free-radical homopolymerization. By comparing results from several different functionals (PBE, M06-2X, wB97XD, KMLYP, and MPW1B95), in conjunction with a series of basis sets (6-31G(d,p), 6-31+G(d,p), 6-31G(2df,p), 6-311G(d,p), 6-311+G(d,p), 6-311+G(2df,p), 6-311+G(2df,2p)), we show that calculations using M06-2X/6-311+G(2df,p)//B3LYP/6-31G(2df,p) provide an activation energy of 5.25 kcal mol(-1) for the homopropagation step, which is within 1 kcal mol(-1) of the experimental value. However, this method predicts a heat of polymerization of 17.37 kcal mol(-1) that is larger than the experimental value by 3.5 kcal mol(-1). MPW1B95/6-311+G(2df,p) on the B3LYP/6-31G(2df,p) geometries produces a heat of polymerization value within 1 kcal mol(-1) of experimental data, yet overestimates the activation energy by 3 kcal mol(-1). In addition, we evaluated the performance of ONIOM MO:MO calculations on the geometry optimization of species comprising our MMA polymerization model and found that ONIOM(B3LYP/6-31G(2df,p):B3LYP/6-31G(d)) is capable of producing geometries in very good agreement with the full B3LYP/6-31G(2df,p) calculations. Subsequent calculations of energies using M06-2X/6-311+G(2df,p) based on the ONIOM geometries provided an activation energy value comparable to that based on the full B3LYP/6-31G(2df,p) geometries.
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Guozhen
authors.initials: G
authors.lastname: Zhang
authors.affiliation: The Dow Chemical Company, 2301 N. Brazosport Blvd., Freeport, Texas 77541, United States.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Konstantinov
authors.affiliation: The Dow Chemical Company, 400 Arcola Rd., Collegeville, Pennsylvania 19426, United States.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Arturo
authors.affiliation: The Dow Chemical Company, 1776 Building, Midland, Michigan 48674, United States.
authors.forename: Decai
authors.initials: D
authors.lastname: Yu
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Broadbelt