Critical evaluation of propagation rate coefficients for free-radical polymerization of functional methacrylic acid esters with this kp data being derived from pulsed-laser initiated polymerizations in conjunction with polymer molecular weight analysis by size-exclusion chromatography
Modeling of free-radical polymerizations is important for science and industry. Unfortunately rather different parameter values are reported for ostensibly the same systems. For measurement of individual propagation rate coefficients, kp, the IUPAC Working Party on “Modeling of Polymerisation Kinetics and Processes” recommended pulsed-laser initiated polymerization (PLP) in conjunction with size-exclusion chromatography (SEC) as the method of choice. This technique has been successfully used to determine reliable propagation rate coefficients for several monomers. After having established benchmark value data of kp for styrene, methyl methacrylate, and other alkyl methacrylates in three previous publications of the IUPAC Working Party, the intention of the present project is to continue this task and to collate reliable kp data for methacrylates with functional, cyclic, and branched ester groups. The knowledge of kinetic data for these monomers is of great importance, as they are frequently used in technical polymerizations, e.g. in the automotive industry.
Special attention has to be paid to the determination of absolute molecular weight distributions (MWD), because propagation rate coefficients are calculated from characteristic (inflection) points of the MWDs. Therefore, the accuracy of kp is directly determined by the accuracy of SEC calibration. Usually SEC calibration standards are not available for these systems, and thus, the knowledge of Mark-Houwink constants is required to apply universal SEC calibration. kp results from ESR spectroscopy and rate measurements will be collected, too. These data are independent of SEC calibration. After critical evaluation of the existing rate coefficients, and after perhaps carrying out several additional experiments, benchmark value data for the functional methacrylates will be published.
project completed see related publications