Liquid crystalline copolyester

Figure 17 Differential scanning colorimetric trace of the liquid crystalline copolyester of 8-(3-phenyl hydroxy) octanoic acid and paro-hydroxy benzoic acid.

Quantitative Small-Angle Light Scattering of Liquid Crystalline Copolyester Films... 

Various process steps were used to determine their Influence on the morphological nature of liquid crystalline copolyester films. Compression molding was used to form quiescent films, while extenslonal deformation above and below the onset of fluidity, as well as shear deformation above the onset of fluidity was used to make non-quies-cent films. It Is a basic result that molecular orientation can only be achieved when the deformation is done while the polymer is In a liquid crystalline melt state. Experimental details are given In the subsection Materials and Processing, while an interpretation is offered in the discussion in the subsection Morphological and Process Consideration. ... 

A few series of azo and azoxy group containing liquid crystalline copolyesters were prepared by limura and coworkers and their phase transition temperatures were examined. No unusual phenomena were found, although monotropic mesophases were observed for the following copolyesters, depending on the combinations and fractions of alkylene groups ... 

Various liquid crystalline copolyesters (LCP s) were used depending on the particular thermoplastic matrix which was selected. In this work three high performance matrices were used polyether-... 

Kinetics of Phase Segregation in Thermotropic Liquid-Crystalline Copolyester and Polyether Imide Blends... 

In a previous paper (1), phase segregation by spinodal decomposition in mixtures of polyethylene terephthalate and polyhydroxybenzoic acid copolymer (PET-PHB) and polycarbonate (PC) has been investigated. It was shown that thermally induced phase segregation takes place above the Tg of PC and exhibits a lower critical solution temperature (LCST). However, the phase separated domains do not grow until the temperature exceeds 255°C. Some disclinations developed within the liquid crystal rich regions. Even in the pure PET-PHB component, four dark brushes with negative sense of disclinations form around 240°C, indicating the presence of nematic liquid crystals. Paci and coworkers (2) claimed that a smectic-nematic transition exists near 270°C in this liquid crystalline copolyester. 

A forced mixture of PET with a liquid-crystalline copolyester (LCP) of ethylene terephthalate and... 

Blackwell J, Biswas A, Gutierrez GA, Chivers RA (1985) X-ray analysis of the structure of liquid-crystalline copolyesters. Faraday Disc. Chem. Soc. 79 73 see also Chivers RA, Blackwell J, Gutierrez GA (1984) Polymer, 25 435... 

Figure 2. Chemical modification of PET via a melt transesterification reaction with p-acetoxybenzoic acid, to obtain a liquid-crystalline copolyester.

J. L. Brewbaker and W. B. Marshall. Liquid crystalline copolyesters of 4-hydroxybenzoic acid and substituted 4-hydroxybenzoic acids. US Patent 5 268 443, assigned to The Dow Chemical Company (Midland, Ml), December 7, 1993. 

W. Grasser, H.-W. Schmidt, and R. Giesa. Fibers spun from poly(ethyl-ene terephthalate) blended with a thermotropic liquid crystalline copolyester with non-coplanar biphenylene units. Polymer, 42(21) 8517-8527, October 2001. 

R Sukananta and S. Bualek-Limcharoen. In situ modulus enhancement of polypropylene monofilament through blending with a liquid-crystalline copolyester. J. Appl. Polym. Sci., 90 1337-1346, 2003. 

S. Saikrasun, S. Bualek-Limcharoen, S. Kohjiya, and K. Urayama. Thermotropic liquid-crystalline copolyester/thermoplastic elastomer in situ composites. I. Rheology, morphology, and mechanical properties of extruded strands. J. Appl. Polym. ScL, 89 2676-2685, 2003. 

S. Saikrasun and T. Amomsakchai. Phase behavior and properties of in situ-reinforcing elastomer composites based on thermoplastic elastomers and thermotropic liquid crystalline copolyester. J. Appl. Polym. ScL, 101 1610-1619, 2006. 

S. C. Tjong, R. K. Y. Li, and X. L. Xie. Compatibilizing effect of styrene-maleic anhydride copolymer on the properties of polyamide-6/liquid crystalline copolyester composites. J. Appl. Polym. ScL, 77 1964-1974,2000. 

HBA/PET 80/20 a liquid crystalline copolyester composed of 80 mole percent p-hydroxy-benzoic acid [HBA] and 20 mole percent PET. 

Blizard, K. G., and D. G. Baird. 1987. The morphology and rheology of polymer blends containing a liquid crystalline copolyester. Polymer Engineering and Science 27 653-662. 

Although the monomers 1-V contain preset monomer sequences, they are destroyed and randomized during polymerization at elevated temperatures, leading to the formation of random copolyesters. Such randomizations were proved to occur in the preparation of other liquid crystalline copolyesters[4,5]. Moreover, utilization of high molecular weight monomers minimizes the loss of reactants through volatilization during polymerization. 

From practical considerations, two properties are of prime interest The effect of liquid crystalline behavior on viscosity and the ability of the polymer to retain the ordered arrangement in the solid state. Liquid crystalline behavior during the melt results in lower viscosity, because the rigid polymeric mesophases align themselves in the direction of the flow. As a result, the polymer is easier to process. Also, retention of the arrangement upon cooling yields a material with greatly improved mechanical properties. Several thermotropic liquid crystalline copolyesters are now available commercially. 

Yerlikaya Zekeriya, Aksoy Serpil, Bayramli Erdal. (2001). Synthesis and Characterization of Fully Aromatic Thermotropic Liquid-Crystalline Copolyesters Containing m-hydroxybenzoic Acid Units J. Polym. Sci. A, 39(19), 3263-3277. 

Pazzagli Federico, Paci Massimo, Magagnini Pierluigi, Pedretti Ugo., Como Carlo, Bertolini Guglielmo, Veracini Carlo, A. (2000). Effect of Polymerization Conditions on the Microstmcture of a Liquid Crystalline Copolyester. J. Appl. Polym. Sci., 77(1), 141-150. 

Wang Jiu-fen, Zhang Na., Li Cheng-Jie. (2005). Synthesis and Study of Thermotropic Liquid-Crystalline Copolyester. PABA.ABPA.TPA. Polym. Mater. Sci. Technol, 21(1), 129-132. 

Method of Producing Thermotropic Liquid Crystalline Copolyester, Thermotropic Liquid Crystalline Copolyester Composition Obtained by the Same Composition US Patent 6268419. International Patent Catalogue C 08 K 5/51. 

Dong Dewen, Ni Yushan, Chi Zhenguo. (1996). Synthesis and Properties of Thermotropic Liquid-Crystalline Copolyesters Containing Bis-(4-oxyphenyl)Methanone. II. Copolyesters from Bis-(4-oxyphenyl)Methanone, Terephthalic Acid, n-oxybenzoic Acid and Resorcene. Po/>wi. (2), 153-158. 

Teoh, M. M., Liu, S. L., Chung, T. S. (2005). Effect of Pyridazine Structure on Thin-Fihn Polymerization and Phase Behavior of Thermotropic Liquid Crystalline Copolyesters. J. Polym. Sci. B, 43(16), 2230-2242. 

Chen Yanming. (1998). The Study of Liquid-Crystalline Copolyesters PHB/PBT, Modified with HQ-TRA. J. Fushun Petrol. Inst, 18(1), 26-29. 

Liu Yongjian, Jin Yi., Bu Haishan, Luise Robert, R., Bu Jenny. (2001). Quick Crystallization of Liquid-Crystalline Copolyesters Based on Polyethyleneterephthalate. J. 

Flores, A., Ania, F., Balta Calleja, F. J. (1997). Novel Aspects of Microslructure of Liquid Crystalline Copolyesters as Studied by Microhardness Influence of Composition and Temperature. Polym, 38(21), 5447-5453. 

Bharadwaj Rishikesh, Boyd Richard H. (1999). Chain Dynamics in the Nematic Melt of an Aromatic Liquid Crystalline Copolyester A Molecular Dynamics Simulation Study. J. Chem. Phys, 1(20), 10203-10211. 

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