Theoretical studies on bond dissociation enthalpies for model compounds of typical plastic polymers

Huang, Jinbao; Zeng, Guisheng; Li, X S; Cheng, Xiaocai; Tong, Hong

doi:10.1088/1755-1315/167/1/012029

Cited by 36 publications

(11 citation statements)

References 23 publications

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“…42 The result of most thermal depolymerization processes, even for single-stream feedstocks, is a diverse product mixture of solids (char), liquids, and gases, with each phase containing their own distribution of products. 42 43 Even if polymers are separated, decomposition studies have also reported wide variations in rates of depolymerization. Apparent activation barriers for depolymerization of PE, PP, and PS have been reported across incredibly broad ranges from 163-303 kJ/mol, 83-285 kJ/mol, and 83-323 kJ/mol, respectively.…”

Section: Reaction Engineering For Polymer Deconstructionmentioning

confidence: 99%

Chemical and biological catalysis for plastics recycling and upcycling

et al. 2021

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At the molecular level, polymers are long chains in which the emergent material properties are dictated by the movement, arrangement, and interactions of these chains. Key factors that contribute to how the polymer chains move and rearrange are the molecular identity and arrangement, crystallinity, and molecular weight. Generally, the monomer identity influences the final application of the polymer by dictating many properties, such as the glass transition temperature (Tg). 12 As the Tg represents a softening of the material, it is a prime factor in determining the final polymer application. Flexible molecules in the backbone, which can relax faster, may result in low Tg materials with applications such as PE bags or rubber (i.e. polybutadiene). 13 Meanwhile, rigid molecules or molecules that result in stronger interchain interactions (and relax on longer timescales) can result in high Tg materials, ideal for reinforced applications. In general, when materials are at temperatures below the Tg, the polymer chains are kinetically arrested, exhibiting higher strengths. Even though monomer identity is often the largest contribution to Tg, it is not the only factor, as molecular weight, 14 tacticity, 15 and crystallinity 16 also contribute. While nearly all polymers exhibit a Tg characteristic of their amorphous region, semi-crystalline polymers will also exhibit concomitant melting behaviour crystalline in their crystalline regions, making them semi-crystalline. Crystallinity has a direct impact on polymer properties, as increases in crystallinity augment the strength of the final product and reduce the permeability of liquids and gases. Co-monomers (e.g., isophthalic acid in poly(ethylene terephthalate) (PET)) are often used to lower or completely remove crystallinity to make polymers easier to process or more transparent. 17 Finally, molecular weight, and the distributions of molecular weights, have some effect on the thermomechanical polymer properties (e.g., increasing molecular weight leads to higher Tg, modulii, etc.). However, over a critical molecular weight, nearly all thermomechanical polymer properties are constant. The exception to this generalization is the viscosity of a polymer melt, which scales with the molecular weight to the 3-3.5 power (η ~ MW 3-3.5 ) and also encapsulates properties such as diffusivity. These factors together contribute to polymer recalcitrance by limiting polymer mobility and accessibility to chemical linkages, posing a challenge for catalytic plastics deconstruction.

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Section: Reaction Engineering For Polymer Deconstructionmentioning

confidence: 99%

Chemical and biological catalysis for plastics recycling and upcycling

et al. 2021

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“…213 However, some bonds are sensitive to the visible range as well. The average bond enthalpy for the CC double bond in conjugated molecules is 614 kJ/mol, whereas the enthalpy for the C−C bond is 348 kJ/mol, 214 from which one can estimate the enthalpy contribution of the π−π interaction to be 266 kJ/mol. This estimated energy of the π−π bond is vulnerable to excitation by light at wavelengths up to 450 nm (2.75 eV).…”

Section: Exciton-induced Chemical Dynamicsmentioning

confidence: 99%

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems

Dimitriev

2022

Chem. Rev.

109

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The exciton, an excited electron–hole pair bound by Coulomb attraction, plays a key role in photophysics of organic molecules and drives practically important phenomena such as photoinduced mechanical motions of a molecule, photochemical conversions, energy transfer, generation of free charge carriers, etc. Its behavior in extended π-conjugated molecules and disordered organic films is very different and very rich compared with exciton behavior in inorganic semiconductor crystals. Due to the high degree of variability of organic systems themselves, the exciton not only exerts changes on molecules that carry it but undergoes its own changes during all phases of its lifetime, that is, birth, conversion and transport, and decay. The goal of this review is to give a systematic and comprehensive view on exciton behavior in π-conjugated molecules and molecular assemblies at all phases of exciton evolution with emphasis on rates typical for this dynamic picture and various consequences of the above dynamics. To uncover the rich variety of exciton behavior, details of exciton formation, exciton transport, exciton energy conversion, direct and reverse intersystem crossing, and radiative and nonradiative decay are considered in different systems, where these processes lead to or are influenced by static and dynamic disorder, charge distribution symmetry breaking, photoinduced reactions, electron and proton transfer, structural rearrangements, exciton coupling with vibrations and intermediate particles, and exciton dissociation and annihilation as well.

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“…The cross-linked PET undergoes chain scission, decarbonylation, and condensation/dehydrogenation reactions during carbonization. 16,25 The chain scission of the C-O bond on the ester group through decarbonylation to release CO/CO2 is associated with the materialization of cross-linking to form high carbon content solid hydro char. Figure S2 shows the FT-IR spectra, and the presence of the carbonyl ester group (C=O) at wave number ~1740 cm -1 (position: 4) confirms the C-O bond scission into ester groups and further decarbonylation to hydro char from PET.…”

Section: Resultsmentioning

confidence: 99%

Role of Cyclopentyl methyl ether co-solvent in Improving SEI layer stability in Hard Carbon Anode for Sodium-ion Batteries

Nagmani

Das

Puravankara

2023

Preprint

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The conversion of polyethylene terephthalate (PET) municipal waste via the carbonization process into hard carbon (WPET-HC) delivers a high-performing, low-cost, sustainable anode material for sodium-ion batteries (SIBs). To further optimize the anode, electrolytes and interfacial chemistry are critical in improving cycling stability and rate capability. Herein, cyclopentyl methyl ether (CPME), a weakly solvating and a wide temperature solvent, is used as an alternative co-solvent to ethylene carbonate (EC) to deliver a high initial coulombic efficiency (ICE) up to 75%. The larger interlayer spacing, low surface area, and slit-shaped micro and mesoporous presence in the WPET-HC structure enhance the low potential plateau capacity to 68%, showing a more battery-type anode material from plastic trash. The WPET-HC delivered the excellent reversible capacity of 356 mAh g-1 at the current density of 30 mA g-1 with superior cycling of 91% after 100 cycles using CPME-PC-based electrolyte. The reduction of CPME co-solvent forms a more inorganic SEI than EC-generated SEI, providing a stable and thin SEI layer boosting the ICE and cycling stability of the anode. The low-temperature battery metric for CPME-PC-based electrolytes showed ~30% added capacity and improved ICE value compared to EC-PC-based electrolytes. The CPME-PC-based electrolyte maintained the higher capacity retention of 88% and 74% at 10℃ and 0℃, respectively, with a coulombic efficiency of 100%, revealing the excellent stability of the electrolyte with the HC anode. The work provides an eco-friendly approach to developing hard carbons from plastic trash and reports for the first time the use of greener, low-solvating CPME in improving the reversible capacity and ICE for low-temperature applications of SIBs.

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Theoretical studies on bond dissociation enthalpies for model compounds of typical plastic polymers

Cited by 36 publications

References 23 publications

Chemical and biological catalysis for plastics recycling and upcycling

Chemical and biological catalysis for plastics recycling and upcycling

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems

Role of Cyclopentyl methyl ether co-solvent in Improving SEI layer stability in Hard Carbon Anode for Sodium-ion Batteries

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