Critically evaluated rate coefficients for free-radical polymerization, 3. Propagation rate coefficients for alkyl methacrylates

Beuermann, Sabine; Buback, Michael; Davis, Thomas P.; Gilbert, Robert G.; Hutchinson, Robin A.; Kajiwara, Atsushi; Klumperman, Bert; Russell, Gregory T.

doi:10.1002/1521-3935(20000801)201:12<1355::aid-macp1355>3.0.co;2-q

Cited by 285 publications

(226 citation statements)

References 21 publications

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“…Willemse and van Herk [53] exploited the advantage that MALDI-MS truly separates species according to their mass no matter whether they are branched or not and performed the determination of k p in acrylate polymerization, in which substantial branching occurs due to backbiting reactions [54]. The results demonstrate that the k p value increases with the size of the acrylate ester moiety, consistent with findings for methacrylates [55]. Following the recommendation described above [52], these authors also worked in the limit of high termination rate, using the position of the PLP peak maximum to determine k p .…”

Section: Propagation Rate Coefficientssupporting

confidence: 65%

Elucidation of Reaction Mechanisms: Conventional Radical Polymerization

Buback

Russell

Vana

2011

Mass Spectrometry in Polymer Chemistry

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It is often remarked that the molar mass distribution (MMD) of a polymer contains the entire history of its synthesis. It is because of this truism that those interested in the kinetics of polymerization are driven to understand polymer MMDs. As will be seen in this chapter, in the case of (conventional) radical polymerization (RP), this quest has been enormously advanced by the advent of large-molecule mass spectrometry (MS), for it is a characterization technique that furnishes hitherto unimaginable detail about the MMD of a polymer, and thus it may be used to elucidate or confirm the mechanisms of RP in many ways that simply were not previously possible.What is it that is so special about an MMD yielded by MS? It is not the distribution amount, for size exclusion chromatography (SEC) already makes a superior fist of measuring that, mostly through the use of refractive-index (RI) detection. Admittedly there can be issues with this, for example, that RI is molar mass dependent for oligomers [1]. However, such issues apply only in particular circumstances, and they pale beside the general uncertainty one must attach to polymer amounts as returned via MS: there is no doubt that SEC is a vastly superior technique in this respect. Rather, what is so special about MS is its delivery of the MMD variable, namely molar mass, M. The two important aspects here are mass accuracy and mass resolving powerFor many large-molecule studies, it is the mass accuracy of MS that is revolutionary. Indeed, the knee-jerk reaction of most RP workers would be that this is also the case in their field. In fact, the matter is not so straightforward. A good illustrative example of this is the pulsed-laser polymerization (PLP) method for measuring propagation rate coefficients, k p [3, 4], which requires knowledge of absolute values of M. By now an enormous quantity of accurate k p data has been yielded by this method, almost all of it through the use of SEC [5,6]. This evidences that for the study of RP kinetics and mechanisms, accurate SEC calibration is commonly possible, either directly through the use of standards, or indirectly through the additional use of Mark-Houwink parameters (so-called universal calibration). So, it is not this aspect alone that makes MS so useful.In fact what is so groundbreaking about MS for the study of RP mechanisms is its mass resolving power, that is, the ability of mass analyzers to separate and measure small differences in M, by now to well under 1-Dalton level with most instruments. As Barner-Kowollik et al. expressed it, this gives the power to visualize the individual polymer chains present in a given sample [7]. Thus, for example, polymer chains of identical degree of polymerization but with a different end group can be resolved, something of which SEC will never (in general) be capable. Because of the accurate determination of the M of the resolved species, their precise chemical composition may be deduced, and from this the mechanism of polymer formation can be inferred. Numerous examples of this ge...

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Section: Propagation Rate Coefficientssupporting

confidence: 65%

Elucidation of Reaction Mechanisms: Conventional Radical Polymerization

Buback

Russell

Vana

2011

Mass Spectrometry in Polymer Chemistry

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“…The difference in values for BMA homopolymer can be eliminated by applying the principle of universal calibration to the RI-PS results using known Mark-Houwink parameters. 18 The agreement seen for BA homopolymer is in accord with previous work showing no significant difference in elution times for poly(butyl acrylate) and PS samples of low MW. 6 The copolymer MW averages calculated by RI-PS are also within 10% of the values measured by LS.…”

Section: Methodsmentioning

confidence: 99%

“…, is well-fit by 18 At 138°C, depropagation begins to affect the rate of methacrylate chain growth, especially at lower monomer concentrations, 8 a point that will be considered later in the model development. As discussed in detail elsewhere, 5,9,11 intramolecular transfer (Scheme 1) complicates the determination of k p for BA.…”

Section: Model Developmentmentioning

confidence: 99%

High-Temperature Semibatch Free Radical Copolymerization of Butyl Methacrylate and Butyl Acrylate

Grady

Hutchinson

2004

Ind. Eng. Chem. Res.

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105

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Acrylic copolymers produced via high-temperature solution polymerization are the base resin component for many automotive coatings. These polymers are often manufactured using a semibatch starved-feed reactor policy in order to tightly control copolymer composition and molecular weight. The combination of high temperature and low monomer concentration greatly promotes the importance of secondary reactions, causing observed conversion and molecular weight profiles to deviate significantly from those predicted by classic free radical kinetics. Although the effects of methacrylate depropagation and acrylate branching and scission have been studied during the homopolymerizations of butyl methacrylate and butyl acrylate, there is little knowledge as to how these mechanisms interact during copolymerization. In this work, we experimentally investigate the effect of monomer feed ratio on molecular weight and conversion profiles for high-temperature semibatch solution copolymerization of butyl methacrylate and butyl acrylate. A mechanistic model, constructed and implemented in Predici, provides a good fit to the experimental data set without any tuning of kinetic coefficients or other parameters. IntroductionThe objective of kinetic modeling is to build a description of how polymer architecture and polymerization rate depend on reaction conditions (temperature, pressure) and species concentrations from a defined set of kinetic mechanisms. This kinetic representation is a critical component of larger-scale process models used to predict the influence of operating conditions on reaction rate and polymer properties, guide (along with appropriate experimentation) the selection and optimization of standard operating conditions for existing and new polymer grades, guide process development from laboratory to pilot-plant to full-scale production, help to discriminate between kinetic and physical (e.g., heat and mass transfer) effects, perform design and safety studies, train plant personnel, and understand and optimize transitions and other dynamic behavior (i.e., process control). Harmon Ray pioneered the development of a sound mathematical framework for treatment of polymerization kinetics 1 so that they could be coupled with detailed models of the physical complexities inherent to many polymerization systems. 2 These efforts were instrumental to the developing field of polymer reaction engineering and also provided important motivation for the development of new experimental techniques to accurately measure polymerization rate coefficients, which to that point suffered from order of magnitude uncertainty. 3,4

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“…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.…”

Section: Introductionmentioning

confidence: 99%

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

2015

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Throughout the last 25 years, computational chemistry based on quantum mechanics has been applied to the investigation of reaction kinetics in free radical polymerization (FRP) with growing interest. Nowadays, quantum chemistry (QC) can be considered a powerful and cost-effective tool for the kinetic characterization of many individual reactions in FRP, especially those that cannot yet be fully analyzed through experiments. The recent focus on copolymers and systems where secondary reactions play a major role has emphasized this feature due to the increased complexity of these kinetic schemes. QC calculations are well-suited to support and guide the experimental investigation of FRP kinetics as well as to deepen the understanding of polymerization mechanisms. This paper is intended to provide an overview of the most relevant QC results obtained so far from the investigation of FRP. A comparison between computational results and experimental data is given, whenever possible, to emphasize the performances of the two approaches in the prediction of kinetic data. This work provides a comprehensive database of reaction rate parameters of FRP to assist in the development of advanced models of polymerization and experimental studies on the topic.

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Critically evaluated rate coefficients for free-radical polymerization, 3. Propagation rate coefficients for alkyl methacrylates

Cited by 285 publications

References 21 publications

Elucidation of Reaction Mechanisms: Conventional Radical Polymerization

Elucidation of Reaction Mechanisms: Conventional Radical Polymerization

High-Temperature Semibatch Free Radical Copolymerization of Butyl Methacrylate and Butyl Acrylate

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

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