ICTAC Kinetics Committee recommendations for analysis of multi-step kinetics

Vyazovkin, Sergey; Burnham, Alan K.; Favergeon, Loïc; Koga, Nobuyoshi; Moukhina, Elena; Pérez‐Maqueda, Luis A.; Sbirrazzuoli, Nicolas

doi:10.1016/j.tca.2020.178597

Cited by 513 publications

(262 citation statements)

References 162 publications

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“…Yet, science is not a popularity contest, so that a routine followed by the majority is not guaranteed to yield the best or even simply a correct result. As a matter of fact, the method is not among the techniques recommended [3] for advanced kinetic studies. Most of the time, it is employed in materials characterization work that among other quantities reports a number that presumably characterizes an energy barrier to a thermal process under study.…”

Section: Introductionmentioning

confidence: 99%

“…This applies fully to the Kissinger method as its formalism largely oversimplifies the kinetics of the processes it treats. Nowadays, as never before, the kinetics community concerned with thermally stimulated processes has come to realize that these processes are commonly multi-step [3]. As such, they have more than one energy barrier that controls them, so that the temperature dependence of their rates cannot be described by a single activation energy.…”

Section: Introductionmentioning

confidence: 99%

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Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

Vyazovkin

2020

Molecules

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161

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The Kissinger method is an overwhelmingly popular way of estimating the activation energy of thermally stimulated processes studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA), and derivative thermogravimetry (DTG). The simplicity of its use is offset considerably by the number of problems that result from underlying assumptions. The assumption of a first-order reaction introduces a certain evaluation error that may become very large when applying temperature programs other than linear heating. The assumption of heating is embedded in the final equation that makes the method inapplicable to any data obtained on cooling. The method yields a single activation energy in agreement with the assumption of single-step kinetics that creates a problem with the majority of applications. This is illustrated by applying the Kissinger method to some chemical reactions, crystallization, glass transition, and melting. In the cases when the isoconversional activation energy varies significantly, the Kissinger plots tend to be almost perfectly linear that means the method fails to detect the inherent complexity of the processes. It is stressed that the Kissinger method is never the best choice when one is looking for insights into the processes kinetics. Comparably simple isoconversional methods offer an insightful alternative.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

Vyazovkin

2020

Molecules

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161

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“…Figure 8 A shows that polymerization of bulk cyanate ester demonstrates a significant variation of the activation energy with conversion (variation of E α exceeds 60% of average E α ), which is a sign of complex (i.e., multistep) nature of the polymerization process [ 50 ]. The pre-exponential factor values demonstrate a similar variation ( Figure 8 B).…”

Section: Resultsmentioning

confidence: 99%

“…As seen in Figure 8 A, polymerizations of the confined cyanate ester are characterized by significantly smaller variation of activation energy that does not exceed 20% of the respective average E α . Such variation can be considered insignificant so that the processes can be treated kinetically as a single step reaction [ 50 ]. We propose that one of the parallel reactions (i.e., n th -order or autocatalytic), included in the rate Equation (8), might be depressed in confinement conditions, so the polymerization process possesses single rate-limiting step.…”

Section: Resultsmentioning

confidence: 99%

Polymerization Kinetics of Cyanate Ester Confined to Hydrophilic Nanopores of Silica Colloidal Crystals with Different Surface-Grafted Groups

et al. 2020

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This study investigates the kinetics of confined polymerization of bisphenol E cyanate ester in the nanopores of the three types of silica colloidal crystals that differ in the concentration and acidity of the surface-grafted proton-donor groups. In all three types of pores, the polymerization has released less heat and demonstrated a very similar significant acceleration as compared to the bulk process. Isoconversional kinetic analysis of the differential scanning calorimetry measurements has revealed that the confinement causes not only a dramatic change in the Arrhenius parameters, but also in the reaction model of the polymerization process. The obtained results have been explained by the active role of the silica surface that can adsorb the residual phenols and immobilize intermediate iminocarbonate products by reaction of the monomer molecules with the surface silanols. The observed acceleration has been quantified by introducing a new isoconversional-isothermal acceleration factor Zα,T that affords comparing the process rates at respectively identical conversions and temperatures. In accord with this factor, the confined polymerization is 15–30 times faster than that in bulk.

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“…Nowadays, specific commercial software programmes for calculating kinetics parameters such as Kinetics Neo (Netzsch), AKTS (Advanced Kinetic and Technology Solution), Kinetics2015 (GeoIsoChem) are available and can assist researchers in the field of kinetic analysis of the solid state. Since the scope of this review is on the thermal stability of drugs, readers interest in further details about solid-state kinetics can refer to the following references [ 25 , 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of Amorphous Solid Dispersions

Jelić¹

2021

Molecules

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Amorphous solid dispersion drug delivery systems (ASD DDS) were proved to be efficient for the enhancement of solubility and bioavailability of poorly water-soluble drugs. One of the major keys for successful preparation of ASD is the selection of appropriate excipients, mostly polymers, which have a crucial role in improving drug solubility and its physical stability. Even though, excipients should be chemically inert, there is some evidence that polymers can affect the thermal stability of active pharmaceutical ingredients (API). The thermal stability of a drug is closely related to the shelf-life of pharmaceutical products and therefore it is a matter of high pharmaceutical relevance. An overview of thermal stability of amorphous solids is provided in this paper. Evaluation of thermal stability of amorphous solid dispersion is perceived from the physicochemical perspective, from a kinetic (motions) and thermodynamic (energy) point of view, focusing on activation energy and fragility, as well all other relevant parameters for ASD design, with a glance on computational kinetic analysis of solid-state decomposition.

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ICTAC Kinetics Committee recommendations for analysis of multi-step kinetics

Cited by 513 publications

References 162 publications

Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

Polymerization Kinetics of Cyanate Ester Confined to Hydrophilic Nanopores of Silica Colloidal Crystals with Different Surface-Grafted Groups

Thermal Stability of Amorphous Solid Dispersions

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