Liquid crystal copolyesters

Significant advances to this end have been made using primarily liquid crystal copolyesters as the rigid-rod chain in various matrix polymers (2,3). Surprisingly, while cellulose and its derivatives also exhibit LC phenomena... 

Liquid crystal copolyesters were prepared using 4-phenylnaphthalene derivatives with 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, or other aromatic diacids. These materials display an improved balance of low melt viscosity, fast cycle time in molding, high tensile, low thermal expansion coefficient, and thermostability. 

Thermo-oxidative Degradation of Polysulfones, Polyesterketones, Liquid-Crystal Copolyesters [21, 30-39]... 

An equally important observation for the above copolyester LCPs is that the ordered arrangement of polymeric mesophases in the melt is retained upon cooling, which is manifested in greatly improved mechanical properties (see Figure 5.5b). The liquid crystalline behavior is therefore advantageous from the standpoint of both processing and properties. Thermotropic liquid crystal copolyesters of structures similar to (I) are now available commercially. 

The high strength high-modular fiber with increased thermo- and fire-resistance can be formed from liquid-crystal copolyester containing 5-95 mol % of M-oxybenzoic acid. 

Liquid crystal copolyesters have been synthesized [50-56] on the basis of -acetoxybenzoic acid, acetoxybisphenol, terephthalic acid and... 

The thermotropic liquid-crystal copolyesters can be S5mthesized also on the basis of -oxybenzoic and 2,6-ox5maphthoic acid at presence of catalysts (sodium and calcium acetates) [69, 70], The catalyst sodium acetate accelerates the process of synthesis. Calcium acetate accelerates the process only at high concentration of the catalyst and influences on the morphology of complex copolyesters. 

It was found that the use of 30% liquid-crystal copolyester of n-oxy-benzoic acid/polyethyleneterephthalate makes polymethylmethacrylate 30% more durable and increases the elasticity modulus on 110%, with the reprocessibility being the same. 

The thermotropic liquid-crystal copolyester of polyethyleneterephthal-ate and terephthaloyl-bis(f2-oxybenzoate) was described in Ref [137], The snapshots of polarized microscopy revealed that copolyester was nematic liquid-crystal one. 

George, E., Porter, R. (1988). Depression of the Crystalnematic Phase Transition in Thermotropic Liquid Crystal Copolyesters. J. Polym. Sci., 26(1), 83-90. 

Shumsky, V. F. Getmanchuk, I. P, Rosovitsky, V F., Lipatov, Yu. S. (1996). Rheological, Visco-Elashc and Mechanical Properties of Mixes of Polymethylmethacrylate with Liquid-Crystal Copolyester Filled with Wire-hke Monocrystals. In Abstracts of the 18-th Symposium on Rheology. Karacharovo, 115. [in Russian]. 

Mi Yongh, Zheng Sixun, Chan Chi-ming, Guo Qipeng. (1998). Mixes of Phe-nolphthalenin with Thermotropic Liquid-Crystal Copolyester. J. Appl. Polym. Sci., 69(10), 1923-1931. 

S. Jenkins, V. Thammongkol, and M. B. Polk, Synthesis and spinning of a thermotropic liquid crystal copolyester containing a semirigid cycloaUphatic spacer, Journal of Polymer Science Part A Polymer Chemistry, 36, 1473 (1998). 

I. Campoy, M. A. Gomez, and C. Marco, Thermogravimetric analysis of blends based on nylon 6 and a thermotropic liquid crystal copolyester. Journal of Thermal Analysis, 52, 705... 

Liquid crystal copolyesters have been S5rnthesized [50-56] on the basis of -acetoxybenzoic acid, acetoxybisphenol, terephthalic acid and m-acetoxybenzoic acid by means of polycondensation in melt. All the copolyesters are thermotropic and form nematic phase. The t5rpes of LQPs of -oxybenzoic acid are given in Table 7.2. 

Fig. 27. Microstructures of liquid crystal copolyesters obtained in polarized light showing the variation of orientation with position in (a) polymer X of a degree of polymerization greater than 100. (Photograph courtesy of T. J. Lemmon, Department of Materials Science and Metallurgy, Pembroke Street, Cambridge.) (b) polymer XI with a degree of polymerization of approximately 50. ...

A typical shear thinning behavior as well as a decrease in viscosity and an increase in the melt flow index while increasing the content of thermotropic liquid crystal copolyester was recorded. In addition, the oriented and ordered fibril structure of thermotropic liquid crystal copolyesters generated in the poly(ethylene 2,6-naphthalate) matrix is illustrated in Figure 6.2. 

The properties of liquid-crystal copolyesters based on -oxybenzoic acid and oxynaphthoic acid (in various ratios and temperatures) are described in Refs. [76-81], It was shown therein that the plates from such polymers formed by die casting are highly anisotropic which results in appearance of the layered structure. Those nematic liquid crystals had ferroelectric ordering. Following substances are characterized in Refs. [82-85] aromatic copolyesters of -oxybenzoate/bisphenol A those based on -oxybenzoic acid, bisphenol... 

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