Critically evaluated rate coefficients in radical polymerization – 7. Secondary-radical propagation rate coefficients for methyl acrylate in the bulk

Abstract

Propagation rate coefficient (k p) data for radical polymerization of methyl acrylate (MA) in the bulk are critically evaluated and a benchmark dataset is put forward by a task-group of the IUPAC Subcommittee on Modeling of Polymerization Kinetics and Processes. This dataset comprises previously published results from three laboratories as well as new data from a fourth laboratory. Not only do all these values of k p fulfill the recommended consistency checks for reliability, they are also all in excellent agreement with each other. Data have been obtained employing the technique of pulsed-laser polymerization (PLP) coupled with molar-mass determination by size-exclusion chromatography (SEC), where PLP has been carried out at pulse-repetition rates of up to 500 Hz, enabling reliable k p to be obtained through to 60 C. The best-fitand therefore recommended-Arrhenius parameters are activation energy E A ¼ 17.3 kJ mol À1 and pre-exponential (frequency) factor A ¼ 1.41 Â 10 7 L mol À1 s À1. These hold for secondary-radical propagation of MA, and may be used to calculate effective propagation rate coefficients for MA in situations where there is a significant population of mid-chain radicals resulting from backbiting, as will be the case at technically relevant temperatures. The benchmark dataset reveals that k p values for MA obtained using PLP in conjunction with MALDI-ToF mass spectrometry are accurate. They also confirm, through comparison with previously obtained benchmark k p values for n-butyl acrylate, methyl methacrylate and n-butyl methacrylate, that there seems to be identical familytype behavior in n-alkyl acrylates as in n-alkyl methacrylates. Specifically, k p for the n-butyl member of each family is about 20% higher than for the corresponding methyl member, an effect that appears to be entropic in origin. Furthermore, each family is characterized by an approximately constant E A , where the value is 5 kJ mol À1 lower for acrylates.

Mechanism of supplemental activator and reducing agent atom transfer radical polymerization mediated by inorganic sulfites: experimental measurements and kinetic simulations

“…39,63–67 Although the presence of water can influence the value of k p , 68 this effect was neglected due to low water content in the studied polymerization systems. Solvent effects on k add could also be neglected since in ATRP initiators are typically quickly consumed at the onset of the reaction.…”

On the Use of Quantum Chemistry for the Determination of Propagation, Copolymerization, and Secondary Reaction Kinetics in Free Radical Polymerization

“…Since its invention in the late 1980s, PLP-based techniques have substantially improved the quality of the experimental measurements of rate parameters in FRP, particularly for propagation reactions. These techniques have also been widely used for the study of the homopolymerization and copolymerization of various monomers [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Radical Polymerization of Alkyl 2-Cyanoacrylates

“…Consequently, PLP is now the International Union of Pure and Applied Chemistry (IUPAC) preferred method for k p determination [64]. Table 4 gives a comparison of experimentally measured k p for n -butyl 2-cyanoacrylate and other common monomers using PLP, and the reader is directed to benchmark Arrhenius parameters in authoritative reports [64,65]. It is difficult to draw direct comparisons between k p values obtained from the rotating sector method and those obtained by PLP, since variations in experimentally reported k p values from different studies can reflect differences in data interpretation and the dependence of kinetic parameters on polymerization conditions.…”