Critically Evaluated Rate Coefficients for Free‐Radical Polymerization, 4

Abstract

a Part 1-3: cf. ref. [2][3][4] bThe publication of this article has been accelerated because of its topical or highly competitive nature.

Determination of Propagation Rate Coefficient of Acrylates by Pulsed‐Laser Polymerization in the Presence of Intramolecular Chain Transfer to Polymer

“…Nowadays, pulsed‐laser polymerization (PLP) with molecular‐weight distribution (MWD) analysis of the resulting polymer by size exclusion chromatography (SEC) has become the method of choice for the evaluation of the propagation rate coefficient, k p , in free radical polymerization. The PLP‐SEC method developed by Olaj et al1 has been applied successfully to many monomers2,3 and has resulted in IUPAC benchmark values for styrene4 and methacrylates 5–7…”

Isothermal and non-isothermal polymerization of methyl methacrylate in presence of multiple initiators

“…For example, a lot of effort has been devoted to correlate k p and k t to the degree of conversion, molecular weight, free volume or chain-end mobility [8,14,27,28,40,43,[64][65][66][67]. These fundamental approaches could not be applied successfully to the case of non-isothermal conditions, which are instead commonly used in the industrial practice.…”

Low Conversion 4‐Acetoxystyrene Free‐Radical Polymerization Kinetics Determined by Pulsed‐Laser and Thermal Polymerization

“…In particular, PLP combined with analysis of the resulting polymer molecular weight distribution (MWD) by size‐exclusion chromatography (SEC) provides a direct estimate of k p , the propagation rate coefficient. This PLP‐SEC experimental technique, pioneered by Olaj and coworkers,7,8 has emerged as the method of choice for studying free‐radical propagation kinetics, as documented in a series of benchmark papers for styrene,9 methacrylates,10–12 and butyl acrylate13 by an IUPAC working party studying free‐radical polymerization kinetics. Coote and Davis14 have also applied the technique to the study of propagation kinetics for a series of 4‐ X ‐styrene ( X = methoxy, methyl, fluoro, chloro, and bromo) monomers in the temperature range of 20–40 °C, an effort closely related to the work described in this publication.…”

“…With known values for t 0 and [ M ], Equation (1) yields a direct estimate of k p . Consistency checks for reliable values are the occurrence of a secondary inflection point located at twice the molecular weight of the first inflection point, and the invariance of measured k p with experimental parameters such as laser pulse repetition rate and energy, and photoinitiator type and concentration 11,12…”

“…Thus, considerable attention has been devoted to the SEC technique used to measure MWD. The success of the effort is demonstrated by the good agreement in k p values measured independently in research laboratories around the world as part of the IUPAC effort 9–13. Generally, this measurement is done using a single detector (differential refractive index, or RI) SEC system using the principle of universal calibration.…”