Kinetic analysis and reaction mechanism of p-alkoxybenzyl alcohol ([4-(hydroxymethyl)phenoxymethyl]polystyrene) resin pyrolysis: Revealing new information on thermal stability

• Published in: Polymer degradation and stability Vol. 189; p. 109606
• Main Authors: Janković, Bojan, Manić, Nebojša
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.07.2021; Elsevier BV
• Subjects: alcohols; Autocatalysis; Benzene fragments; Benzoquinone; benzoquinones; Chain scission; Cleavage; Dehydrogenation; Depolymerization; Epoxy resins; Homolytic cleavage; Kinetics; Mathematical models; nitrogen; Parameter estimation; peptides; Polymerization; Polystyrene resins; polystyrenes; prediction; Pyrolysis; Reaction mechanisms; Solid phases; Thermal stability; Wang resin; Pyrolysis; Benzene fragments; Homolytic cleavage; Autocatalysis; Wang resin
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2021.109606

•Novel data about pyrolysis kinetics of PS/DVB type (Wang) resin.•Homolytic cleavage of CC bonds induced by heating represents the weakest links.•Friedman plots analysis showed the existence of accelerated reaction by the product.•It was founded that autocatalytic reaction is less dependent on pyrolysis temperature.•By attacks from free radicals above 360 °C material is vulnerable shortening life-time. This study provides new information on the thermal stability and kinetics of pyrolysis of commonly used resins in solid-phase peptide synthesis. Pyrolysis process of 4-benzyloxybenzyl alcohol resin was monitored by simultaneous TGA-DTG measurements in a nitrogen atmosphere, at four different heating rates (5, 10, 20 and 30 K min−1). Kinetic computations included the model-free (isoconversional) and model-based methods for reliable estimation of kinetic parameters and the mechanism of investigated process. Based on the findings from applied methods, the pyrolysis process can be described by three reaction steps, where one of them encompasses the consecutive reactions. The first step (n-th order reaction, referred to Fn) is attributed to the random scission of the main chain in PS (polystyrene) solid support, where polymer radicals were formed. The second step proceeds through homolytic cleavage path of ether linkage of the resin (by the first-order reaction, referred to F1) and then via phenoxy radical (semiquinone) formation which is converted into the benzoquinone through a dehydrogenation (by autocatalysis reaction, referred to Cnm). Finally, the third step (referred to Fn reaction) was characterized by depolymerization mechanism, which takes place at higher temperatures (T > 385 °C). With determined kinetic parameters and the most probable mechanism functions, the model agrees excellently with experimental data. By applying the obtained kinetic results, isothermal life-time prediction was also performed.