Wholly aromatic liquid-crystalline polyesters

Han, Haesook; Bhowmik, Pradip K.

doi:10.1016/s0079-6700(96)00028-7

Cited by 106 publications

(53 citation statements)

References 115 publications

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“…Liquid distillates formed during their prepolymerizations were quantitatively analyzed by 1 H NMR with integration. The distillates were >95% acetic acid, and were obtained in 93-96% of the amount expected if all the acetic anhydride in the feed came back as acetic acid in the distillate.…”

Section: Nmr Analysis Of Distillates Formed During Prepolymerizationmentioning

confidence: 99%

“…The sublimate had been washed with acetone to remove the smallest molecules, and nothing dissolved in CDCl 3 for an NMR spectrum. The results of NaOD/D 2 O treatment followed by 1 H NMR with integration are given in Table 9. The sublimate was deficient in P and had extra T, causing a large imbalance with extra carboxyl groups.…”

Section: Analysis Of a Sublimate From An Lcp Polymerizationmentioning

confidence: 99%

“…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%

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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: Nmr Analysis Of Distillates Formed During Prepolymerizationmentioning

confidence: 99%

Section: Analysis Of a Sublimate From An Lcp Polymerizationmentioning

confidence: 99%

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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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“…[1][2][3] They are typically prepared by the solution or interfacial polymerization reaction between dicarboxylicacid chlorides and diols, 4,5 and an acid or phenyl ester exchange reaction of the acetate or ester of the acids under severe conditions (high temperature and reduced pressure). Thermally stable PEs derived from isophthalic and terephthalic acids with bisphenol-A have been commercialized.…”

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confidence: 99%

Synthesis and Characterization of Novel Organosoluble, Thermal Stable and Optically Active Polyesters Derived from 5-(2-Phthalimidiylpropanoylamino)isophthalic Acid

Mallakpour

Rafiee

2007

Polym J

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ABSTRACT:A new aromatic diacid monomer containing pendent L-alaninephthalimide group was synthesized in three steps in high yield and purity. Several new, highly soluble and optically active aromatic polyesters containing phthalimide and flexible chiral groups were prepared with moderate molecular weights by direct polycondensation with tosyl chloride (TsCl), pyridine (Py) and N,N-dimethylformamide (DMF) as condensing agent. The aim of this work was to obtain novel optically active polyesters that were more soluble in common organic solvents while maintaining the high thermal stability. All polymers derived from such a diacid and aromatic diols were highly organosoluble in the solvents like N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, DMF, Py and dimethyl sulfoxide. These new optically active polyesters with inherent viscosities ranging from 0.21 to 0.81 dL/g were obtained with high yields. Thermogravimetric analysis (TGA) data showed that these polyesters are thermal stable, with 10% weight loss being recorded above 370 C. Some of the above polymers were characterized by 1 H-NMR, FT-IR, elemental analyses and specific rotation techniques. [doi:10.1295/polymj.PJ2007061] KEY WORDS Polyester / Optically Active Polymers / TsCl/Py/DMF Condensing Agent / Thermal Properties / Solubility / Direct Polycondensation / Polyesters (PE)s are significant class of high performance and engineering macromolecules, which find utilize in a number of various applications.

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Wholly aromatic liquid-crystalline polyesters

Cited by 106 publications

References 115 publications

Structural Analysis of Aromatic Liquid Crystalline Polyesters

Structural Analysis of Aromatic Liquid Crystalline Polyesters

Mechanism Studies of LCP Synthesis

Synthesis and Characterization of Novel Organosoluble, Thermal Stable and Optically Active Polyesters Derived from 5-(2-Phthalimidiylpropanoylamino)isophthalic Acid

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