Thermal stability of phenolic resin: new insights based on bond dissociation energy and reactivity of functional groups

Bian, Cheng; Wang, Shujuan; Liu, Yuhong; Jing, Xinli

doi:10.1039/c6ra07597e

Cited by 29 publications

(18 citation statements)

References 74 publications

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“…For example, BDE values are used to predict relative reaction rates using well-established Evans-Polanyi-type correlations with bond strengths in radical hydrogen atom abstractions 2 . BDEs also provide insight into thermodynamically accessible reaction mechanisms for a given compound, and their calculation is often the first step in characterizing dominant pathways in combustion 3 , polymer synthesis 4 and thermal stability 5,6 , lignin depolymerization 7 , drug metabolism [8][9][10] , explosives 11 , organic synthesis planning 12,13 , and other applications to energy-related materials 14 .…”

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confidence: 99%

Prediction of organic homolytic bond dissociation enthalpies at near chemical accuracy with sub-second computational cost

et al. 2020

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Bond dissociation enthalpies (BDEs) of organic molecules play a fundamental role in determining chemical reactivity and selectivity. However, BDE computations at sufficiently high levels of quantum mechanical theory require substantial computing resources. In this paper, we develop a machine learning model capable of accurately predicting BDEs for organic molecules in a fraction of a second. We perform automated density functional theory (DFT) calculations at the M06-2X/def2-TZVP level of theory for 42,577 small organic molecules, resulting in 290,664 BDEs. A graph neural network trained on a subset of these results achieves a mean absolute error of 0.58 kcal mol −1 (vs DFT) for BDEs of unseen molecules. We further demonstrate the model on two applications: first, we rapidly and accurately predict major sites of hydrogen abstraction in the metabolism of drug-like molecules, and second, we determine the dominant molecular fragmentation pathways during soot formation.

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confidence: 99%

Prediction of organic homolytic bond dissociation enthalpies at near chemical accuracy with sub-second computational cost

et al. 2020

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“…Their increased occurrence can be explained by the symmetrical structure of Antioxidant 2246 and cleavage of the methylene bridge. It was found that the CC bond strength in methylene bridges of methanediyldiphenols is weakest in o‐o’ derivatives ( o ‐ o ’ < o ‐ p ’ < p – p ’) , and indeed the products are formed through benzylic cleavage in two positions (cf. Fig.…”

Section: Resultsmentioning

confidence: 99%

Thermal Stability of Polymer Additives: Comparison of Decomposition Models Including Oxidative Pyrolysis

Bartsch

Girard

Wilde

et al. 2018

Vinyl Additive Technology

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The thermo‐oxidative stability of widely used polymer additives has been investigated. A comparative analytical approach with classic and innovative decomposition models for polymer additives was conducted and the results supported using quantum‐chemical calculations. Unique pyrolysis products of the analytes were compiled utilizing pyrolysis online coupled to gas chromatography followed by mass spectrometric detection (Pyr‐GC–MS). The pyrolysis was either performed under inert conditions or in an oxygen‐containing atmosphere. Squalane was applied as polymer‐mimicking liquid next to low density polyethylene (LDPE) and polyamide 6 (PA 6) as matrices for 10 selected additives. The additives included in this study range from antioxidants and plasticizers to processing aids. These were selected to address a range of application in consumer products and to cover different chemical classes. The toxicological relevance of additives and potential breakdown products was considered. Consequently, degradation of sterically hindered antioxidants, diarylamines, and a trimellitic acid derivative was investigated. The findings were used to predict the behavior of consumer products made of polymeric materials entailing additives. The level of Antioxidant 2246 [2‐tert‐butyl‐6‐[(3‐tert‐butyl‐2‐hydroxy‐5‐methylphenyl)methyl]‐4‐methylphenol] and one of its predicted decomposition products was determined in baby bottle nipples made of natural rubber [2‐tert‐butyl‐4‐methylphenol] utilizing the complementary technique of gas chromatography coupled to tandem mass spectrometry (GC–MS/MS). This study provides a comprehensive characterization of important polymer additives and enables the prioritization of degradation products for further risk assessment. J. VINYL ADDIT. TECHNOL., 25:E12–E27, 2019. © 2018 The Authors. Journal of Vinyl and Additive Technology published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers

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“…Zhong et al proved that the HO· radicals, peeled from the phenolic structure or generated from radical exchanged reactions, had high concentration and significantly destructive effect during the initial pyrolysis of PR. Our previous study also indicated that the frontier orbitals of HO· and BPF match well and have the potential to react with each other. From the above analyses, it can be speculated that HO· may have destructive effect on the initial decomposition of BPF, and from another perspective, the introduction of HO· maybe effective in degradation of BPF.…”

Section: Introductionmentioning

confidence: 61%

“…The reactivity analyses will be helpful for determining which BPFs or which sites of the BPFs are vulnerable to HO· attack. The main basis of this part are: (i) During the initial stage of hydrogen abstraction or free radical addition reactions, the free radical is firstly attracted by the electrostatic potential; (ii) Frontier orbitals match well is the prerequisite for the title reactions; (iii) When the radicals and target group are close enough, the electron population began to overlap and Fukui function will be more precise to present the reactivity of functional groups …”

Section: Resultsmentioning

confidence: 99%

“…The HOMO/LUMO analysis will be helpful to determine whether the frontier orbitals between the BPF molecules and HO· match well. The previous study showed that the singly occupied molecular orbital (SOMO) of HO· is characteristic of π‐type orbital. From Supporting Information Figures S4 and S5, it can be found that both the HOMO and LUMO isosurfaces near the hydroxyls and benzenes in BPF molecules are π‐type orbitals and symmetrical to the SOMO of HO·.…”

Section: Resultsmentioning

confidence: 99%

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Initial reaction mechanism between HO· and bisphenol‐F: Conformational dependence and the role of nonbond interactions

Bian

Wang

et al. 2017

Int J of Quantum Chemistry

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Hydroxyl radical (HO·) plays an important role in the initial pyrolysis of hydroxyl-containing polymers, such as phenolic resin (PR). In this study, the reaction mechanism between HO· and bisphenol-F (BPF) or tetra-methyl substituted BPFs, which were taken as the model molecules of PR, was studied with the density functional theory approach. The results based on the Fukui function and reduced density gradient function showed that, both the hydroxyls and the carbon atoms in the phenolic groups are the reactive sites for HO· attack. The hydroxyls are most likely to be attacked by HO· owing to the strong electrostatic potential around the hydroxyls and the low reaction barriers, especially for cis-o-o' type BPF. The strong pAp (CHAp and OHAp) interaction between the phenolic rings in BPF leads to decreased conjugative effect of the phenolic rings, which further lead to decreased addition barriers and reaction rate constant. K E Y W O R D S bisphenol-F, conformation, density functional theory, hydroxyl radical, reaction mechanism 1 | I N T R O D U C T I O N Bis(hydroxyphenyl)methanes, also named as bisphenol-Fs or BPFs, are a group of chemical compounds with two hydroxyphenyl functionalities bridged by one methylene group ( Figure 1). Owing to the structurally similarity to bisphenol-A, BPFs are desirable materials with many attractive applications paralleling bisphenol-A in use, such as the primary raw materials of epoxy, polycarbonate, or phenolic resins, but considerably lower toxicity than bisphenol-A. [1] However, the widespread application of BPFs also leads to considerable environmental problems. [2] A detailed investigation on the thermal decomposition mechanism of BPFs will be conducive to guiding the application and degradation of BPFs in reasonable ways. In particular, BPFs can also be regarded as the basic structural units or model compounds for phenolic resins (PRs), which are generally made from phenol and formaldehyde. [3] Hence, the elucidation of the thermal decomposition mechanism of BPF will be helpful for understanding the relationship of structural-thermal stability of PRs.The constitutional and conformational isomerism of BPFs lead to multiple structural characteristics of BPFs. There are three constitutional BPF isomers, 2,2 0 -bis(hydroxyphenyl)methane, 2,4 0 -bis(hydroxyphenyl)methane, and 4,4 0 -bis(hydroxyphenyl)methane (Figure 1), and this is also the primary reason for the rather complex crosslinked structure of PR. Wang et al.'s computational results [4] showed that there are more than 24 stable conformers of o-o' type BPF. Pillsbury et al. [5] stated that owing to the hydrogen bonds and OHAp interaction formation, the conformers with hydroxyls paralleled or perpendicular to each other are the dominant structures. Gruber et al. [6] proved that a p-p 0 type BPF conformer with the C 2 symmetry has the lowest energy, leading to a strong crystallinity of p-p 0 type BPF. In the highly crosslinked network of cured PR, most of the BPF-like structures are four methylene substituted BPFs, this fu...

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Thermal stability of phenolic resin: new insights based on bond dissociation energy and reactivity of functional groups

Abstract: Based on bisphenol-F-like model molecules, the bond dissociation energies and Fukui function were calculated to interpret the relationship between the atomistic structure and thermal properties of the phenolic resin.

Cited by 29 publications

References 74 publications

Prediction of organic homolytic bond dissociation enthalpies at near chemical accuracy with sub-second computational cost

Prediction of organic homolytic bond dissociation enthalpies at near chemical accuracy with sub-second computational cost

Thermal Stability of Polymer Additives: Comparison of Decomposition Models Including Oxidative Pyrolysis

Initial reaction mechanism between HO· and bisphenol‐F: Conformational dependence and the role of nonbond interactions

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