Propagation and Termination Constants in Free Radical Polymerization

High‐Temperature Propagation and Termination Kinetics of Styrene to High Conversion Investigated by Electron Paramagnetic Resonance Spectroscopy

“…This behavior can be traced back to the conversion-dependences of k t and f. The drop in the radical concentration occurring at the maximum is caused by a dramatic decrease in f, which in this conversion range is greater than the corresponding relative decrease in k t . The gradual shift of the peak towards higher conversion with temperature suggests that the dramatic fall in f shifts in the same way, consistent with the experimentally obtained f versus conversion data at 70 (reference [7]) and 120 8C ( Figure 6). The value of f for 2,2 0 -azobisisobutyronitrile (AIBN) during bulk polymerization of St has been shown to increase with temperature (in the temperature range 40-80 8C) over a wide conversion range.…”

“…Accurate determination of k p and k t has now become possible as a result of improvements in the electron paramagnetic resonance (EPR) method [1][2][3] and the development of pulsed-laser polymerization (PLP) techniques. [4][5][6] Although the situation has improved in recent years, [7] most of the experimental data on k p and k t (and also the initiator efficiency (f)) are concerned with polymerization at low conversion.…”

Determination of the Propagation Rate Coefficient of Vinyl Pivalate Based on EPR Quantification of the Propagating Radical Concentration

“…Recent advances in methodology have allowed determination of consistent k p values. [1] Size exclusion…”

Polymerization of acrylamide in styrene containing inverse microemulsions: polymerization kinetics and polymer product composition studies

“…To evaluate the polymerization and (co)polymerization kinetics, it is necessary to consider the nature of the monomers involved with respect to their polymerization rate constants14–16 in addition to the partitioning of the monomers and initiators between the oil and water phases of the inverse microemulsion. Thus, for example, if initiator radicals cannot escape from the water pools of the inverse micelles and enter the oil phase, their role must take over monomer, solvent or emulsifier radicals which can be formed by addition or transfer reactions of monomer, solvent or emulsifier with radicals generated from APS.…”

“…The extent of the above‐mentioned initiation mechanism depends on the concentration of the monomer present in the water pools or entering the water pools of the inverse micelles (closely related to the solubility of S in the water pools), the rate of monomer initiation in the water pools and the exit rate of the monomer radicals formed. It follows from the values of the ratios of propagation and termination rate constants k p / k t 0.5 for AAm14 (4.72 mol −0.5 dm 1.5 s −0.5 at 25 °C) and S14, 15 (1.95 × 10 −2 mol −0.5 dm 1.5 s −0.5 at 50 °C and 2.15 × 10 −2 mol −0.5 dm 1.5 s −0.5 at 60 °C) that AAm will polymerize at a substantially higher rate than S. Reactivity ratios for copolymerization of AAm (monomer 1) and S (monomer 2) are16 r 1 = k p11 / k p12 = 0.33 and r 2 = k p22 / k p21 = 1.49. This means that both monomers readily copolymerize.…”