Free radical polymerization of ethyl methacrylate and ethyl α-hydroxy methacrylate: A computational approach to the propagation kinetics

• Published in: Polymer (Guilford) Vol. 53; no. 15; pp. 3211 - 3219
• Main Authors: Dogan, Berna, Catak, Saron, Van Speybroeck, Veronique, Waroquier, Michel, Aviyente, Viktorya
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 06.07.2012; Elsevier
• Subjects: Applied sciences; Copolymerization; entropy; Entropy of activation; Ethanol; Ethyl alcohol; Exact sciences and technology; Fiber reinforced plastics; Free radical polymerization; hydrogen bonding; hydrophobic bonding; Modeling; Monomers; Organic polymers; Physicochemistry of polymers; polymerization; polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Propagation (polymerization); Solvent effect; Solvents; Toluene; Solvent effect; Modeling; Free radical polymerization; Mass copolymerization; Solution copolymerization; Experimental study; Chemical reaction kinetics; Alcohol copolymer; Methacrylic derivative copolymer; Ethyl methacrylate copolymer; Density functional method; Radical copolymerization; Activation energy; Reaction propagation
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.05.018

The propagation kinetics of ethyl methacrylate (EMA) and ethyl α-hydroxy methacrylate (EHMA) has been subject to a computational study to understand their free radical polymerization (FRP) behavior in bulk and in solution using Density Functional Theory (DFT). The propagation of EHMA is studied in ethanol and toluene to assess the effect of hydrogen-bonding solvents on FRP of monomers with α-hydroxy functionality. Although EMA and EHMA resemble each other in structure, EHMA propagates faster in bulk due to the presence of intermolecular hydrogen-bonds, which tend to facilitate the approach of the propagating species. This falls in contrast with the experimentally observed lower propagation rates of EHMA in ethanol compared to toluene. Calculations show that the 2.28 rate acceleration in toluene is governed by the ratio of the pre-exponential factors, which reflect the entropies of activation, in both media. The polar protic solvent ethanol has a disruptive effect via hydrogen-bonding on the 6-membered ring shape of EHMA monomers thus decreasing the entropy of activation of the reaction. In the case of toluene, there are no special interactions with the hydrophobic solvent, the entropy of activation is higher than in ethanol. [Display omitted]