Synthetic and thermodynamic investigations in the polymerization of ethylene carbonate

Vogdanis, Lazaros; Martens, Barbara; Uchtmann, H.; Hensel, F.; Heitz, Walter

doi:10.1002/macp.1990.021910301

Cited by 149 publications

(142 citation statements)

References 10 publications

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“…[66] The chromium-salen catalyst 1 a-Cl along with the reduced model 1 b-Cl used in many of the calculations is depicted in Figure 1. Calculations were carried out with 1 b if not stated otherwise.…”

Section: Theoretical Studymentioning

confidence: 99%

On the Formation of Aliphatic Polycarbonates from Epoxides with Chromium(III) and Aluminum(III) Metal–Salen Complexes

Luinstra

Haas

Molnár

et al. 2005

Chemistry A European J

210

136

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A DFT-based description is given of the CO2/epoxide copolymerization with a catalyst system consisting of metal (chromium, iron, titanium, aluminum)-salen complexes (salen = N,N'-bis(3,5-di-tert-butylsalicyliden-1,6-diaminophenyl) in combination with either chloride, acetate, or dimethylamino pyridine (DMAP) as external nucleophile. Calculations indicate that initiation proceeds through nucleophilic attack at a metal-coordinated epoxide, and the most likely propagation reaction is a bimolecular process in which a metal-bound nucleophile attacks a metal-bound epoxide. Carbon dioxide insertion occurs at a single metal center and is most likely the rate-determining step at low pressure. The prevalent chain terminating/degradation-the so-called backbiting, a reaction leading to formation of cyclic carbonate from the polymer chain-would involve attack of a carbonate nucleophile rather than an alkoxide at the last unit of the growing chain. The backbiting of a free carbonato chain end is particularly efficient. Anion dissociation from six-coordinate aluminum is appreciably easier than from chromium-salen complexes, indicating the reason why in the former case cyclic carbonate is the sole product. Experimental data were gathered for a series of chromium-, aluminum-, iron-, and zinc-salen complexes, which were used in combination with external nucleophiles like DMAP and mainly (tetraalkyl ammonium) chloride/acetate. Aluminum complexes transform PO (propylene oxide) and CO2 to give exclusively propylene carbonate. This is explained by rapid carbonate anion dissociation from a six-coordinate complex and cyclic formation. CO2 insertion or nucleophilic attack of an external nucleophile at a coordinated epoxide (at higher CO2 pressure) are the rate-determining steps. Catalysis with [Cr(salen)(acetate/chloride)] complexes leads to the formation of both cyclic carbonate and polypropylene carbonate with various quantities of ether linkages. The dependence of the activity and selectivity on the CO2 pressure, added nucleophile, reaction temperature, and catalyst concentration is complex. A mechanistic description for the chromium-salen catalysis is proposed comprising a multistep and multicenter reaction cycle. PO and CO2 were also treated with mixtures of aluminum- and chromium-salen complexes to yield unexpected ratios of polypropylene carbonate and cyclic propylene carbonate.

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Section: Theoretical Studymentioning

confidence: 99%

On the Formation of Aliphatic Polycarbonates from Epoxides with Chromium(III) and Aluminum(III) Metal–Salen Complexes

Luinstra

Haas

Molnár

et al. 2005

Chemistry A European J

210

136

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“…As a consequence, random poly(ether carbonate)s of low molecular weights are formed instead. [3][4][5][6][7] In the past, our group reported on the preparation of highmolecular-weight polyurethanes by the copolymerization Summary: Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2-propylene carbonate (PC, 2) leading to a polyurethane (M n ¼ 12 200; M w 18 400; M w =M n ¼ 1.50) with a T m of 145.7 8C and a T g of 53.7 8C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate.…”

Section: Introductionmentioning

confidence: 99%

Copolymerization of Ethylene Carbonate and 1,2‐Propylene Carbonate with Tetramethylene Urea and Characterization of the Polyurethanes

Ubaghs¹,

Novi²,

Keul³

et al. 2004

Macro Chemistry & Physics

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Summary: Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2‐propylene carbonate (PC, 2) leading to a polyurethane ($\overline M _{\rm n}$ = 12 200; $\overline M _{\rm w}$ 18 400; $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.50) with a Tm of 145.7 °C and a Tg of 53.7 °C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well‐underlined mechanism for the copolymerization is proposed. Furthermore, TeU is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU‐EC‐stat‐TeU‐PC) by increasing the PC/EC ratio in the feed. 13C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in Tm with increasing PC content.Tm was found to decrease with increasing PC content.imageTm was found to decrease with increasing PC content.

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“…However, the reaction conditions in polymerization studies [5][6][7][8][9][10][11][12] are typically selected to allow for a total conversion of the compound on a reasonable time scale, requiring high reaction rates, so that the reaction rate close to room temperature is not relevant for polymer science, but it can be of interest for the lithium-ion cell chemistry. Probably the most thorough analysis with a base initiator was carried out by Lee and Litt,12 who studied the polymerization mechanism of ethylene carbonate using KOH as initiator at 150 -200…”

mentioning

confidence: 99%

Hydrolysis of Ethylene Carbonate with Water and Hydroxide under Battery Operating Conditions

Metzger

Strehle

Solchenbach

et al. 2016

J. Electrochem. Soc.

118

150

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This study deals with the decomposition of ethylene carbonate (EC) by H 2 O in the absence and presence of catalytically active hydroxide ions (OH − ) at reaction conditions close to lithium-ion battery operation. We use On-line Electrochemical Mass Spectrometry (OEMS) to quantify the CO 2 evolved by these reactions, referred to as H 2 O-driven and OH − -driven EC hydrolysis. By examining both reactions at various temperatures (10 -80 • C) and water concentrations (<20 ppm or 200, 1000, and 5000 ppm H 2 O) with or without catalytically active OH − ions in EC with 1.5 M LiClO 4 , we determine an Arrhenius relationship between the CO 2 evolution rate and the cell temperature. While the apparent activation energy for the base electrolyte (<20 ppm H 2 O) is very large (app. E a ≈153 kJ/mol), substantially lower values are obtained in the presence of H 2 O (app. E a ≈99 ± 3 kJ/mol), which are even further decreased in the presence of catalytically active OH − (app. E a ≈43 ± 5 kJ/mol). Our data show that OH − -driven EC hydrolysis is relevant already at room temperature, whereas H 2 O-driven EC hydrolysis (i.e., without catalytically active OH − ) is only relevant at elevated temperature (≥40 • C), as is the case for the base electrolyte. Thus, catalytic quantities of OH − , e.g., from hydroxide contaminants on the surface of transition metal oxide based active materials, would be expected to lead to considerable CO 2 gassing in lithium-ion cells. Lithium-ion battery electrolytes typically rely on the cyclic carbonate ethylene carbonate (EC) as a co-solvent, mixed with linear carbonates like diethyl carbonate (DEC), dimethyl carbonate (DMC), and/or ethyl methyl carbonate (EMC) and a lithium salt, usually lithium hexafluorophosphate (LiPF 6 ). EC has unique properties in terms of the formation of a solid-electrolyte interphase (SEI) at the negative electrode (typically graphite) in lithium-ion batteries (LIBs). Upon the electrochemical reduction of EC, ethylene gas is released and lithium ethylene dicarbonate (LEDC) is deposited on the surface of the negative electrode, forming an SEI that prevents further electrolyte reduction but at the same time still allows for Li + -ion conduction. [1][2][3][4] Compared to the numerous articles dealing with the electrochemical decomposition of EC, it is rarely discussed in battery literature that EC can also undergo chemical decomposition reactions.In principle, all cyclic monomers can undergo ring-opening reactions followed by polymerization. It has been shown in the polymer literature that the five-membered aliphatic cyclic carbonates, such as ethylene carbonate and propylene carbonate, can be polymerized using Lewis acids, transesterification catalysts, or bases as initiators. [5][6][7][8][9][10][11][12] There is a consensus among most authors that CO 2 is lost during the polymerization of EC and that the repeat units of the resultant polymers are a mixture of carbonate units and the corresponding oxide units. When Lewis acids (e.g., Al(acac) 3 or Ti(OBu) 4 ) 5,6 or transester...

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Synthetic and thermodynamic investigations in the polymerization of ethylene carbonate

Cited by 149 publications

References 10 publications

On the Formation of Aliphatic Polycarbonates from Epoxides with Chromium(III) and Aluminum(III) Metal–Salen Complexes

On the Formation of Aliphatic Polycarbonates from Epoxides with Chromium(III) and Aluminum(III) Metal–Salen Complexes

Copolymerization of Ethylene Carbonate and 1,2‐Propylene Carbonate with Tetramethylene Urea and Characterization of the Polyurethanes

Hydrolysis of Ethylene Carbonate with Water and Hydroxide under Battery Operating Conditions

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