Critically evaluated rate coefficients for free-radical polymerization Part 6: Propagation rate coefficient of methacrylic acid in aqueous solution (IUPAC Technical Report)

Abstract

Critically evaluated propagation rate coefficients, kp, for free-radical polymerization of methacrylic acid, MAA, in aqueous solution are presented. The underlying kp values are from two independent sources, which both used the IUPAC-recommended technique of pulsed-laser-initiated polymerization (PLP) in conjunction with molar mass distribution (MMD) analysis of the resulting polymer by size-exclusion chromatography (SEC). Different methods of measuring the MMD of the poly(MAA) samples have, however, been used: (i) direct analysis via aqueous-phase SEC and (ii) standard SEC with tetrahydrofuran as the eluent carried out on poly(methyl methacrylate) samples obtained by methylation of the poly(MAA) samples from PLP. Benchmark kp values for aqueous solutions containing 15 mass % MAA are presented for temperatures between 18 and 89 °C. The Arrhenius pre-exponential and activation energy of kp at 15 mass % MAA are 1.54 × 106 L mol-1 s-1 and 15.0 kJ mol-1, respectively. Also reported are critically evaluated kp values for 25 °C over the entire MAA concentration range from dilute aqueous solution to bulk polymerization.

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

“…Nowadays, PLP coupled with size exclusion chromatography (SEC) is the method recommended by the International Union of Pure and Applied Chemistry (IUPAC) for the measurements of propagation rate coefficients [19][20][21][22]. The propagation rate coefficients for various important monomers evaluated by PLP are listed in Table 1.…”

Solvent Influence on Propagation Kinetics in Radical Polymerizations Studied by Pulsed Laser Initiated Polymerizations

“…[13] For a number of monomers, so-called benchmark data were published. [14][15][16][17][18][19] Application of PLP-SEC also gave access to copolymerization propagation rate coefficients, k p,copo , and thus contributed to a better understanding of the mechanisms controlling the propagation reaction in copolymerizations. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Furthermore, PLP-SEC was used to study heterogeneous systems.…”

“…To improve the situation, over the last couple of years more systematic studies into the solvent influence on k p for various monomers were conducted. In addition to several organic solvents, water [19,[49][50][51][52][53][54][55][56][57][58] and rather unconventional solvents such as supercritical carbon dioxide [59][60][61][62][63][64][65][66] and ionic liquids [67][68][69] were used. Because of the widely differing physico-chemical properties of the solvents, which are significantly different from monomer properties, solvent induced changes were expected to be large, and thus, were expected to contribute to a better understanding of the solvent influence on k p .…”

Modeling of Emulsion Copolymerizations Will it Ever be Possible? Part III Conclusion

“…For water soluble monomers like acrylic and methacrylic acid also reliable data are available now 14,15 . However with water soluble monomers complications arise because the k p values not only depend on pH but also on the monomer and polymer concentration in the aqueous solutions 14,15 .…”

“…However with water soluble monomers complications arise because the k p values not only depend on pH but also on the monomer and polymer concentration in the aqueous solutions 14,15 . A historic account of the developments in the understanding of acrylate kinetics has recently been published in a special issue of Macromolecular Rapid Communications, completely devoted to acrylate chemistry 16 .…”