Thermotropic main chain polyesters

Jin, Jung‐Il; Kang, Chung-Seock

doi:10.1016/s0079-6700(97)00013-0

Cited by 55 publications

(47 citation statements)

References 141 publications

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“…For the end groups (Table 8), the designation begins with the letter representing the aromatic group nearest the end, the second letter is superscripted and identifies the end group (a = acetate, c = carboxyl, p = phenolic hydroxyl), and a further subscripted letter (if present) indicates the next aromatic unit. It should be mentioned that the P aB end group values for the aromatic protons are within experimental area of those for the very similar acetylated monomer P(OAc) 2 and the observed peaks are very likely partly due to the latter compound. The NMR spectra show the presence of cyclic dimers B 2 * and QT*, where * signifies a cyclic oligomer.…”

Section: H Nmr Spectra Of Hfip Extracts Of Prepolymerssupporting

confidence: 61%

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Structural Analysis of Aromatic Liquid Crystalline Polyesters

et al. 2011

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Laboratory preparations of liquid crystalline prepolymers, distillates accompanying prepolymers, final polymers, and sublimates accompanying final polymers were examined. NaOD/D 2 O depolymerization of prepolymers and polymers back to monomers with integration of the 1 H NMR spectra showed up to 6% excess of carboxyls over phenol groups, caused partly by loss of the low-boiling comonomer hydroquinone through distillation during prepolymerization and leaving anhydride units in the polymer chain. ESI − MS and MS/MS of hexafluoroisopropanol extracts of the prepolymer detected small molecules including some containing anhydride groups; ESI + MS showed the presence of small cyclic oligomers. 1 H NMR (including TOCSY) spectra provided more quantitative analyses of these oligomers. The final polymerization increases the length of the polymer chains and sublimes out the small oligomers. Anhydride linkages remaining in the polymer must make LCP's more susceptible to degradation by nucleophilic reagents such as water, alkalis, and amines.

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Section: H Nmr Spectra Of Hfip Extracts Of Prepolymerssupporting

confidence: 61%

“…Their low melt viscosities combined with their excellent mechanical properties make them extremely useful for the fabrication of intricate constructs for numerous optical and electronic devices. Their outstanding flame retardance, solvent resistance, and barrier properties offer still further advantages [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Structural Analysis of Aromatic Liquid Crystalline Polyesters

et al. 2011

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“…Thermotropic main chain LCP copolyesters are an important class of modern high tech polymers [1][2][3]. Their high mechanical strength and modulus, combined with stability to chemicals and heat lend them attractive properties.…”

Section: Introductionmentioning

confidence: 99%

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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“…A wide variety of thermotropic polyesters [1][2][3][4][5][6] have been reported in the past 20 years. Among them Xydar 7,8 and Vectra 9,10 are the best known commercially available thermotropic copolyesters presently being manufactured and marketed by companies in the United States of America.…”

Section: Introductionmentioning

confidence: 99%

“…The structure-property relationships of aromatic polyesters are continuously being explored by many research groups in academia as well as in industries. 6,[11][12][13][14][15][16][17][18][19][20] Especially, the thermal behavior [21][22][23][24][25][26] of copolyesters is known to be very sensitive to their microchemical structure and thermal history. Recently, we 27,28 have demonstrated that the properties of copolyesters depend not only on their overall composition but also on the comonomer sequence along the chain.…”

Section: Introductionmentioning

confidence: 99%