Thermotropic aliphatic-aromatic

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. 

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

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. 

Serbezeanu Diana, Vlad-Bubulac Tachita, Hamciuc Corneliu, and Aflori Magda. Structure and properties of phosphorous-containing thermotropic liquid-crystalline aliphatic-aromatic copolyesters. Macromol. Chem. Phys. 211 no. 13 (2010b) 1460-1471. 

Wojtkonski [185] has also reported on three series of melt spinnable thermotropic aromatic-aliphatic polyimines. The polyimines were prepared by reaction of 1,2-bis(4-formylphenoxy) ethane, terephthalaldehyde, or 4,4 -biphenyldicarboxaldehyde, respectively, with l,n-bis(4-amino-3-methylphenoxy) alkanes where n = 1-10, 12, 14, and 16 in dry DMAC containing 5% dry lithium chloride. The polymers decomposed at 400°C, and as the length of the flexible aliphatic segments increased, melting points decreased. Polymers with an odd... 

By far the largest group of liquid crystalline polymers containing imide groups are copoly(esterimide)s (PEIs). These have been sub-divided into flexible copolymers containing aliphatic spacers and wholly aromatic copolymers. There are several reports of copoly(amide-imide)s and copoly(ether-imide)s (both thermotropic and lyotropic) and these are treated separately. There are only a few examples of wholly aromatic imide containing LCPs, as polyimides frequently melt well above their decomposition temperature. Successful attempts have been made to incorporate flexible spacers, but in most instances the spacers are based on ether units, and the polymer is more strictly classified as a poly(etherimide). 

In (3.65) there is more of an aliphatic component than an aromatic one. Phenylene rings are each isolated by aliphatic components. No mesogenic units of rigid-rods are present in the molecule. However, the thermotropic liquid crystalline phase was observed for many of the polymers although... 

J.D. Sudha, Synthesis and characterization of hydrogen-bonded thermotropic liquid crystalline aromatic-aliphatic poly(ester-amide)s from amido diol, J. Polym. Sci. A Polym. Chem. 38 (2000) 2469-2486. 

In this article, in connection with our previous endeavor, we would like to report synthesis and properties of new copolyesters having ordered comonomer sequences consisting of mesogenic units and polymethylene spacers, i.e., thermotropic aromatic-aliphatic copolyesters having sequentially ordered structures ... 

This family of noncovalently bonded PLCs may also include polyelectrolyte + surfactant complexes which, as will be seen, can also give rise to liquid crystalline mesophases. In these complexes there is only a flexible alkyl chain attached to the ionic head group in the small molecule constituent, with no rigid aromatic core present. Since surfactants themselves are frequently thermotropic liquid crystals, it is not surprising that their complexes with polyelectrolytes may produce PLCs, in both cases driven by the incompatibility between the ionic and aliphatic parts leading to amphitropic systems [27]. 

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... 

A type of aromatic-aliphatic liquid crystalline copolyesters has been synthesized from 2-chlorohydroquinone, 1,4-CHDM and terephthaloyl chloride (Figure 6.14). The CHDM units act in these copolyesters as flexible spacers providing the necessary chain mobility to be thermotropic. The structure and thermal behavior of these copolyesters were characterized by hot-stage polarized light microscopy, SEM, FTIR, NMR, DSC and TGA (57). It has been reported that they are insoluble in common solvents and may form mesophases at temperatures near the melting temperature of PET (58). 

Aromatic imide groups are known to be nearly planar, rigid, polar, and thermostable. However, aromatic imide structures are also known to be non-mesogen in nature. Poly(ester-amide) (PEI) derived from N- (4 -carboxyphenyl) trimellitimide and aliphatic spacers are not thermotropic, whether the spacer used is chiral or not. Semi-aliphatic spacers are observed to exhibit both a smectic and a nematic LC phase in the resultant thermotropic PEIs. The semi-aliphatic chiral spacers exhibit both chiral smectic phase (A or C ) and cholesteric phase. Such a chiral smectic LC-phase, which may be ferroelectric in nature, is extremely rare for LC-main-chain polymers [27]. It is a particular advantage of polar imide mesogens to favor the formation of layer-structures when combined with non-polar species [28]. 

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]. 

What is the discotics for the thermotropic liquid crystals that is the lyotropic chromonic liquid crystals (LCLCs) for the lyotropic materials. LCLC molecules are plank-like rather than rod-like, rigid rather than flexible, aromatic rather than aliphatic. Typical LCLC molecules and their aggregation in... 

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. ... 

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