Propagation rate coefficients from electron spin resonance studies of the emulsion polymerization of methyl methacrylate

Abstract

a) Masuhara, H.; Ohwada, S.; Mataga, N.; Itaya, A.; Okamoto, K.; Kusabayashi, S. Chem. Phys. Lett. 1978,59,188. (b) Masuhara, H.; Ohwada, s.; Mataga, N.; Itaya, A.; Okamoto, K.; Kusabayashi, S. Kobunshi Ronbunshu 1980,37, 275. (4) Tsuchida, A.; Yamamoto, M.; Nishijima, Y. J. Polym. Sci., Polym. Chem. Ed. 1985,23, 585. (5) (a) Iwai, K.; Furue, M.; Nozakura, S.; Shirota, Y.; Mikawa, H. Polym. J. (Tokyo) 1980,12,97. (b) Iwai, K.; Itoh, Y.; Furue, M.; Nozakura, S. J. Polym. Sci., Polym. Chem. Ed. 1983,21, 2439. (6) Tazuke, S.; Yuan, H. L.; Iwaya, Y.; Sato, K. Macromolecules 1981, 14, 267. (7) This value was estimated from the oxidation potential measured by cyclic voltammetry (oxidation potential: El,* = 0.82 V vs. Ag /Ag+ for ECZ, 0.41 V vs. Ag /Ag+ for N,N-dimethylaniline, and 0.08 V vs. Ag/Ag+ for N,N,N',N'-tetramethylbenzidine) on the basis of the result obtained by: Washio, M.; Tagawa, S.; Tabata, Y. Polym. ABSTRACT The first results are reported for the quantitative application of ESR spectroscopy to emulsion polymerization kinetics. When this technique, in conjunction with dilatometric rate measurements, was applied to the seeded emulsion polymerization of methyl methacrylate a t 50 "C, the dependence of the propagation rate coefficient (k,) on the weight fraction of polymer (w,) was found to be k , = k: (0.33 5 wp 5 0.84) and k, = k: exp(-29.8[wP -0.841) (0.84 I wp I 0.99), where kPo = 790 i 300 dm3 mol-' s-l. These results reflect the passage of the latex particles through their glass transition point (at cup = OM), leading to the propagation step being controlled by the diffusion of monomer to the propagation site. The observed decrease in k , for wp > 0.84 appears to be less dramatic than that predicted by current free volume theories.ABSTRACT The character of one-dimensional order in a smectic polymer with mesogenic side groups and long spacers was studied by means of SAXS experiments, polarized microscopy, and electron microscopy over a wide temperature range, including the clearing temperature. It was demonstrated that the electron density distribution along the normal-to-smectic plane is a complicated function, characteristic of three-component systems. Such state is due to microphase separation of different fragments of macromolecules. The damping of correlation in smectic layer arrangements has an exponential form with correlation lengths of 460-600 A.The temperature increase leads to decreasing layer-packing perfection and thermal expansion of interlayer and intralayer packing. In the isotropic state a weak fluctuation of electron density, which was associated with the correlation hole effect, was observed.

Molecular Aspects of Radical Polymerizations—The Propagation Frequency

“…Steadily increasing radical concentrations have also been observed for MMA seeded emulsion polymerizations, either batch or semibatch, and in the presence of a small amount of methacrylic acid. [26,[35][36][37] For emulsion polymerization of MMA, the k p values were found to be independent of the particle size in the diameter range between 80 and 400 nm but within an experimental scatter of about two orders of magnitude. [37] However, for particles of 50 and 500 nm a clear difference in the Arrhenius relations for k p has been found.…”

“…[23] The k p values for other monomers have also been determined, such as for n-butyl methacrylate, [24] vinyl chloride, [25] and MMA. [26] However, the estimation of reaction rate constants from ESR requires careful control of the experimental conditions, see also the critical discussion in ref. [27] Problems may arise, especially for monomers with lower propagation rates, if the sensitivity limitation requires high radical concentrations as discussed by Tonge et al [28] Under such conditions mainly oligomeric radicals exist.…”

Polymerization Processes, 1. Fundamentals

“…The sequence of elementary reactions in Equations (22)(23)(24)(25)(26)(27)(28) result in total radical concentrations of the order 10 À9 -10 À5 mol/L for most commercial polymerizations. Since polymer molecules with high molecular masses are produced from the very start of polymerization, the reacting solution can be quite viscous over most of the monomer conversion range.…”

“…When producing polymers with high molecular masses, the chain-length dependence could be neglected. The propagation rate constant k p is relatively insensitive to the viscosity of the system, except at very high polymer concentrations [13,22].…”

Miniemulsion Polymerization Monitoring Using Off‐Line Raman Spectroscopy and In‐Line NIR Spectroscopy

“…[36] The oligomer size was considered to have the same diameter as a micelle. For the case studied, the surfactant used was sodium lauryl sulfate, whose micelle characteristic radius is 2.6 nm.…”