Critical evaluation of propagation rate coefficients for free-radical polymerization of vinyl esters (vinyl acetate, vinyl pivalate) with this kp data being derived from pulsed-laser initiated polymerizations in conjunction with polymer molar mass analysis.
First-principles modeling of free-radical polymerizations remains an important objective for polymer science and industry, in order to efficiently introduce process modifications and new products. The lack of reliable rate coefficients remains a major impediment in reaching this goal. For measurement of individual propagation rate coefficients, kp, the IUPAC Subcommittee on “Modeling of Polymerization Kinetics and Processes” recommended pulsed-laser initiated polymerization (PLP) in conjunction with size-exclusion chromatography (SEC) as the method of choice. After having established benchmark value data of kp for styrene, and a series of methacrylates (four previous publications from 1995-2003), the Subcommittee has tackled more difficult (faster propagating, with competing side reactions) monomer systems including butyl acrylate, methacrylic acid, and methyl acrylate (three publications from 2004-2013).
The present project will collate reliable kp data for vinyl esters, primarily vinyl acetate but also vinyl pivalate. These vinyl esters have proven difficult to study using the PLP technique due to the relative monomer stability to radical attack. Improved understanding of this difficulty, combined with the utilization of lasers that can operate up to 500 Hz, have led to some recently published results that now allow evaluation and compilation of a benchmark data set. The knowledge of kinetic data for these monomers is of great importance, as they are frequently used in technical polymerizations, e.g. in the coatings and adhesives industries.
May 2014 – Project announcement published in Chem. Int. May-June 2014, p. 13; DOI: 10.1515/ci.2014.36.3.13b
July 2017 update – the following report has been published (first online in Sep 2016) : Critically Evaluated Rate Coefficients in Radical Polymerization – 8. Propagation Rate Coefficients for Vinyl Acetate in Bulk, C. Barner-Kowollik, S. Beuermann, M. Buback, R. A. Hutchinson, T. Junkers, H. Kattner, B. Manders, A. N. Nikitin, G. T. Russell, A. M. van Herk, Macromol. Chem. Phys. 2017, 218, 1600357; https://doi.org/10.1002/macp.201600357
The task group plans to meet at Macro2018 and finalize a second report for Pure Appl Chem.
March 2019 update – A Technical Report titled ‘Critically Evaluated Propagation Rate Coefficients For Radical Polymerization: Acrylates and Vinyl Acetate’ has been submitted to PAC and is under review.
The Report in PAC available AOP, 25 Sep 2019; https://doi.org/10.1515/pac-2018-1108 and in print in the Nov issue, ref PAC, 91(11), pp. 1883-1888, 2019.
Page last update 13 Nov 2019