Free-radical chain generation of ketene during the synthesis of liquid crystalline aromatic polyesters

Stuparu, Mihaiela C.; Xu, Juhua; Hall, H. K.

doi:10.1016/j.tetlet.2009.08.099

Cited by 3 publications

(4 citation statements)

References 9 publications

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“…The elimination of ketene from 4-acetoxyarenes at high temperature has been previously described in the literature [10], leading to the conclusion that the terminal aromatic acetoxy groups are not stable. Recently, we presented evidence for the chain free radical mechanism for this ketene loss [11]. Under these polymerization conditions, ketene could also form from acetic anhydride or a mixed anhydride.…”

Section: Study Of the Small Molecule Productsmentioning

confidence: 95%

Mechanism Studies of LCP Synthesis

Padías

Hall

2011

Polymers

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Abstract:The LCP (Liquid Crystal Polymer) known as Vectra is synthesized by acidolysis of 4-hydroxybenzoic acid with 6-hydroxy-2-naphthoic acid. The apparently simple acidolysis mechanism for LCP polycondensation is in fact a complex blend of mechanisms. Kinetics of model reactions and of actual polycondensations followed second-order kinetics and their rate constants were comparable. In the latter stages, ketene loss leads to phenolic ends, while decarboxylation provides phenyl ester ends. Accordingly, the mechanism changes to phenolysis. A quinone methide intermediate may also intervene, as revealed by kinetics studies and MALDI-TOF spectroscopy. Tailor-made matrices and synthesis of alternating well-defined oligomers assisted our studies. Nucleophilic aromatic substitutions may play a role, and we speculate on possible chain polycondensation. Esterolysis may be a useful alternative to LCP synthesis. Complications caused by ketene loss can be averted by the use of methoxycarbonyloxy monomers.

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Section: Study Of the Small Molecule Productsmentioning

confidence: 95%

Mechanism Studies of LCP Synthesis

Padías

Hall

2011

Polymers

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“…It is at Tucson that I learned about the synthesis of homopolymers and alternating copolymers by free radical polymerization methods. [11] After a one-year position at Tucson, I joined the team of Prof. Siegel at University of Zurich, and it is there that I asked the question: Can I take the corannulene chemistry that is developed in Siegel laboratory and implement it in macromolecular science? Since corannulene is a known electron acceptor, [12,13] will these corannulenebased polymers be good (n-type) materials for organic electronics applications?…”

Section: Introductionmentioning

confidence: 99%

Towards Macromolecular Architectures of Corannulene

Stuparu

2011

Chimia

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In an attempt to introduce corannulene chemistry to macromolecular science, my research program is dedicated to synthetic strategies leading to corannulene-based polymers with interesting architectures and properties. In this brief account, I will discuss the synthesis of a variety of corannulene-based building blocks (monomers) and their utility in the preparation of a wide range of corannulene-rich macromolecular structures.

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“…OCK may also be an intermediate in the radical chain decomposition of acetate groups to form the phenolic end groups. 9 Though unstable under ordinary conditions, OCK has been studied spectrally in an argon matrix. 10 In a separate physical organic chemistry investigation, Cevasco et al 11 studied the reaction of 2,4-dinitrophenyl 4-hydroxybenzoate with aniline in alkaline conditions; on the basis of sophisticated kinetic measurements, they concluded that more anilide was formed than expected.…”

Section: ' Introductionmentioning

confidence: 99%

“…4-Oxo-2,5-cyclohexadienylideneketene (OCK) was proposed to be responsible for both these observations. OCK may also be an intermediate in the radical chain decomposition of acetate groups to form the phenolic end groups . Though unstable under ordinary conditions, OCK has been studied spectrally in an argon matrix …”

Section: Introductionmentioning

confidence: 99%