Thermotropic liquid crystalline polymers for high performance applications

Economy, James; Goranov, Konstantin

doi:10.1007/bfb0021200

Cited by 47 publications

(15 citation statements)

References 28 publications

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“…Hoechst Celanese Vectra A‐950 was used in this investigation. This polymer is comprised of 73 mol % 4‐hydroxybenzioc acid (HBA) and 27 mol % 6‐hydroxy‐2‐naphthoic acid (HNA), and has been studied extensively 1–6, 7–9, 11, 23, 24. Based on X‐ray diffraction study, Vectra A is a random copolymer 33.…”

Section: Methodsmentioning

confidence: 99%

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Revisit the crystallization mechanism of vectra,? a liquid crystal polymer

Chung

Cheng

Goh

et al. 1999

J. Appl. Polym. Sci.

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ABSTRACT:We have studied isothermal transition kinetics and crystallization mechanisms of the Hoechst Celanese liquid crystal polymer Vectra™ A-950 using a differential scanning calorimetry. This material is a random copolymer with a composition made of 73 mol %/27 mol % of HBA (1,4-dihydroxybenzoic acid)/HNA (2,6-dihydroxynaphthoic acid). When comparing our results to previous work on 75/25 HBA/ HNA, we found some similarities as well as dissimilarities. In the case of similarities, both polymers show two types of transition processes in the low-temperature region (below 495 K). One is a fast process, which can be regarded as liquid crystal transition, and is characterized by a heat of fusion that does not vary significantly with annealing time. The other transition is a slow process related to crystal perfection and shows increases in the heat of transition and the transition temperature with increasing annealing time. However, the apparently slight difference in polymer composition also leads to a few surprising results. For example, previous work on 75/25 HBA/HNA two transition peaks (slow and fast processes) were observed after annealing it at 505 K, while in the current work only one transition peak in the case of 73/27 HBA/HNA was observed. In addition, based on the relationship between heat of fusion and annealing time, the LCP made from 73/27 HBA/HNA may perfect faster (in the time scale we study); hence, its posttreatment processes may be accomplished more efficiently than that of 75/25 HBA/HNA. This result also suggests that the former may have a better sequence or a better matching of molecular dimensions for crystallization than that of the latter.

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Section: Methodsmentioning

confidence: 99%

“…They concluded that phase‐separation occurred as a consequence of chain segregation according to the chain length, while self‐organization of textures was strongly depend on the thermal history. The effects of thermal treatment on LCPs have also been reviewed by Economy and Goranov,23 and Jaffe et al24…”

Section: Introductionmentioning

confidence: 99%

Revisit the crystallization mechanism of vectra,? a liquid crystal polymer

Chung

Cheng

Goh

et al. 1999

J. Appl. Polym. Sci.

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“…Conversely, one of the main disadvantages of LC polymers is the fact that they do not exhibit obvious and easily detected mesophases as in the case of small organic LC compounds. Presently, LC polymers are mainly tested as (i) NLO materials, (ii) membranes with penetrability created by an electrical field, (iii) temperature detectors or (iv) materials for nanoelectronics [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Among the various types of LC polymers, two main groups of thermotropic polymers are indicated: 1) polymers with mesogenic groups in the main chain, e.g., polyesters or polyamides (Kevlar) and 2) polymers with mesogenic groups in the side chain, e.g., polyolefins or polysiloxanes.…”

Section: Polyazomethines With Lc Propertiesmentioning

confidence: 99%

An overview of LC polyazomethines with aliphatic–aromatic moieties: Thermal, optical, electrical and photovoltaic properties

Iwan

2015

Renewable and Sustainable Energy Reviews

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“…TLCPs have the potential applications to fabricate protective coatings, adhesives, structural foams and high strength composites. 8 TLCPs are widely used for protective coating in aerospace application wherein the use of current material is difficult. 9 High-molecular-weight polymers are difficult to process due to viscosity.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of thermotropic liquid crystalline polyimides

et al. 2015

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Non-symmetrical and linear dyad-based mesogens were synthesised containing imine or ester bridging group. In the present work, due to the absence of branching in diamine-based mesogen, the structure has-rigidity inversely imine/ester bridging groups between two benzene rings imparts-flexible property to the mesogen and consequently rigid-flexible property has been balanced. The synthesised mesogens were characterized by different techniques including nuclear magnetic resonance and Fourier transform infrared spectroscopy. Liquid crystalline polymers (LCPs) were synthesised using pyromellitic dianhydride and 4-[(4-aminobenzylidene)amino]aniline or 4-aminophenyl-4-aminobenzoate. Subsequently, thermotropic liquid crystalline polymers (TLCPs) have also been evaluated to obtain optical microscopy textures at different temperatures which demonstrated interesting and notable changes. It is worth noting that marble-like textures were observed upto 200 • C.

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Thermotropic liquid crystalline polymers for high performance applications

Cited by 47 publications

References 28 publications

Revisit the crystallization mechanism of vectra,? a liquid crystal polymer

Revisit the crystallization mechanism of vectra,? a liquid crystal polymer

An overview of LC polyazomethines with aliphatic–aromatic moieties: Thermal, optical, electrical and photovoltaic properties

Synthesis and characterization of thermotropic liquid crystalline polyimides

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