Thermotropic aliphatic-aromatic polyesters

Figure 2 (4,5) summarizes some key points on what was the first reported and wel 1-characterized thermotropic polymer. The Eastman workers melt copolymerized p-acetoxybenzoic acid with poly(ethylene terephthalate) (PET) to form a series of thermotropic aliphatic-aromatic polyesters (X7G polymers). Some of these compositions showed the characteristic melt optical anisotropy typical of nematic small molecules, that is, the melt between crossed polaroids on a hot stage microscope transmits light. This nematic order was persistent. Of course, shear birefringence is also shown by isotropic polymer melts but light transmission decay is quite rapid. 

Aromatic thermotropic liquid crystal polyesters (Ar-TLCP s) and TLCP s containing aliphatic linkages can be compatibilized as binary-TLCP blends by transesterification. The morphology and physical properties of the resultant binary-TLCP blend are dependent on the blockiness, composition and viscosity ratios of the two TLCP components. Polycarbonate (PC) can also be blend compatibilized with either TLCP s or binary-TLCP blends, by transesterification of aliphatic linkages from the TLCP s into the PC. In this work, the degree of selective transesterification is quantified and its effect on TLCP blend compatibility is described... 

Perhaps the most obvious characteristic of thermotropic polyesters Is their bulk appearance. These polyesters, whether aliphatic-aromatic as the X7G type or the wholly aromatic structures, all have a fibrous, almost wood-like texture. The fracture surface of a strand shows the typical highly fibrillar morphology. If such a strand Is put through a conventional cutting process, a fuzzy and very fibrillar chip often results. Another plainly visible characteristic of thermotropic polyesters Is the opalescent, almost metalllc-1 Ike surface sheen. 

Novel aromatic-aliphatic biobased polyesters showing thermotropic behavior in the melt have been presented, incorporating different biobased monomers such as 2,5-furandicarbo)ylic acid (2,5-FDCA), suberic acid (SuA), and vanillic acid (VA) in thermotropic L.C. polymers (TLCPs). The chemical structures, molecular weights, phase transitions, thermal behavior, and mechanical performance of the synthesized polymers are studied using polarization optical microscopy, WAXD, DSC, TGA, DMTA, SS NMR spectroscopy, rheology, and tensile tests. These materials show a low temperature transition from the crystalline to the nematic phase, and stable nematic phases up to 300 °C and higher. ... 

THERMOTROPIC POLYESTER -AROMATIC/ALIPHATIC C0P0LYMERS-X7G (EASTMAN)... 

The chemical resistance of polyester amide glass fibre composite is excellent [126]. A solvent mixture of CF3COOH/CHCI3 was used as a solvent for thermotropic LC polyester, based on 4-chlorocarbonyl phenyl esters of aromatic dicarboxylic acids and phenols or aliphatic diols for viscosity measurement. This indicates thermal stability in various organic solvents. [127]. Unsaturated aromatic LC polyesters, synthesized with the aim to fix the LC state, can be crosslinked by using styrene. The crosslinked matrix can be degraded by refluxing in 3 M aqueous sodium hydroxide solution and methanol in a vol. ratio of 3 2 [128]. 

---