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Thermodynamic and Kinetic Considerations in the Copolymerization of Ethylene and Carbon Dioxide
journal contribution
posted on 2006-04-18, 00:00 authored by Craig J. Price, B. Jesse E. Reich, Stephen A. MillerThe thermodynamics of ethylene and carbon dioxide copolymerization are assessed with average
bond dissociation energies, the Benson additivity method, and density functional theory (DFT) calculations (B3LYP
6-31G†). The DFT results suggest that formation of the alternating copolymer is exothermic (ΔH = −4.31 kcal/mol per repeat unit), but endergonic at most temperatures (>−159 °C, the ceiling temperature), and therefore it
is practically inaccessible because of entropic factors. However, these thermodynamic calculations show that the
polymerization is favorable (exergonic) at room temperature (25 °C) when the molar quotient of ethylene/carbon
dioxide exceeds 2.37 (29.7 mol % CO2 or less). Various copolymerization conditions with catalytic amounts of
late transition metal complexes (Fe, Co, Ni, Cu) in combination with MAO (methylaluminoxane) produced
oligomers or polymers containing only ethylene. The lack of ester functionality, as confirmed by mass spectrometry
and 13C NMR, attests to the dubious nature of previous reports claiming up to 30 mol % incorporation of carbon
dioxide.
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molar quotientester functionalityBenson additivity methodcarbon dioxidemass spectrometrycalculations showMAOVarious copolymerization conditionscarbon dioxide copolymerization3LYPbond dissociation energiesCODFT resultsentropic factorsethylene13 C NMRCarbon DioxideKinetic Considerationstransition metal complexes
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