Liquid Crystalline Polyesteramides Research Articles

Effect of Poly(esterimide)s as Compatibilizers on the Physical Properties of Poly(etherimide)/Thermotropic Liquid Crystalline Polymer in-situ Composites

This study investigates the compatibilizing effect of poly(esterimide) (PEsI) on the blend of poly(etherimide) (Ultem 1000; Ultem from General Electric Company) and thermotropic liquid crystalline polyesteramide (Vectra B950; Vectra B from Hoechst Celanese). Two types of polyesterimide (PEsI) were prepared as compatibilizers to improve the interfacial adhesion of incompatible Ultem and Vectra B. Poly(ethyleneterephthalate) (PET) based PEsI (EI10) and poly(butyleneterephthalate) (PBT) based PEsI (BI10) including 10 mol% of the imide are prepared. The binary Vectra B/PEsI and Ultem/PEsI blends were investigated in terms of thermal properties. This revealed that EI10 is more reactive (or compatible) with Vectra B, whereas BI10 is more compatible with Ultem. The effect of compatibilizer structures on the ternary Ultem/Vectra B/PEsI blends was also studied by thermal behavior, rheological properties, and mechanical properties. These results showed that BI10, more compatible with Ultem matrix, acts as a better compatibilizer in a ternary Ultem/Vectra B/PEsI blend system than EI10, more compatible with Vectra B phase. The optimum level of the compatibilzers turned out to be about 1–2 wt% for the blend systems.

Interfacial tension between a liquid crystalline polyesteramide and polypropylene obtained by dielectric spectroscopy

Dielectric spectroscopy is an unexplored technique in the elucidation of the morphology of polymer blends. Especially the appearance of interfacial polarization can reveal important information about the microstructure of a polymer blend. A model system of liquid crystalline polymer fibers lined up in a thermoplastic matrix was investigated. After heating above the melting temperature of both phases, the fibers developed distortions which grew with time. Dielectric spectroscopy was used to follow the change in shape of the distorted fibers. The use of only two frequencies made it possible to increase the number of relevant data points in the initial stages of the fiber breakup process. From these measurements it was possible to calculate the growth rate and hence the interfacial tension between the two polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 815–825, 1998

Interfacial tension between a liquid crystalline polyesteramide and polypropylene obtained by dielectric spectroscopy

Dielectric spectroscopy is an unexplored technique in the elucidation of the morphology of polymer blends. Especially the appearance of interfacial polarization can reveal important information about the microstructure ofa polymer blend. A model system of liquid crystalline polymer fibers lined up in a thermoplastic matrix was investigated. After heating above the melting temperature of both phases, the fibers developed distortions which grew with time. Dielectric spectroscopy was used to follow the change in shape of the distorted fibers. The use of only two frequencies made it possible to increase the number of relevant data points in the initial stages of the fiber breakup process. From these measurements it was possible to calculate the growth rate and hence the interfacial tension between the two polymers.

Effect of Thermal History and Rigid Unit on Rheological Properties of the Thermotropic Liquid Crystalline Polyesteramides

Effect of Thermal History and Rigid Unit on Rheological Properties of the Thermotropic Liquid Crystalline Polyesteramides

Liquid Crystalline Poly(ester amide)s Based on N,N‘-Dimethyldiamines and an Aromatic Ester Triad

A series of thermotropic liquid crystalline poly(ester amide)s was synthesized based on various N,N'-dimethylalkylenediamines and terephthaloyl bis(4-oxybenzoyl chloride), TBOC. Several different synthetic procedures were investigated to synthesize liquid crystalline (LC) polymers having a broad range of molecular weights. The highest molecular weight polymers were obtained by the low-temperature solution condensation of N,N'-bis(trimethylsilyl)diamines and TBOC. Analyses of the polymers by wide angle X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy showed that the as-prepared crystalline polymers melted to form a nematic,liquid crystalline phase, which showed no evidence of recrystallization upon cooling. The LC polyesteramides with a 6-methylene spacer unit exhibited a monotropic behavior in contrast to the polymers or copolymers with a 12-methylene spacer unit which are enantiotropic. Changes in polymer conformation which occurred on heating in the solid state and in the liquid crystalline state were evaluated by solid state 13 C cross polarization magic angle spinning NMR spectroscopy which showed that the polymers had considerable mobility at temperatures well below the crystalline melting point. The polymers, when precipitated from solution, contained mixtures of syn and anti amide units, but after melting, the syn amide unit was exclusively obtained indicating that it is likely the most thermodynamically stable conformation.

Elastic moduli of a liquid crystalline polymer and its in‐situ composites

AbstractThe elastic moduli of a liquid crystalline polyesteramide (LCP) and polycarbonate/LCP in‐situ composites with 10 to 80 wt% of LCP have been measured as functions of draw ratio λ from 1 to 15 by an ultrasonic method. For the LCP, the sharp rise of the axial Young's modulus E3 and the slight decreases of the transverse Young's modulus E1 and the axial (C44) and transverse (C66) shear modulus with increasing λ result from the alignment of chains along the draw direction. E1, C44, and C66 follow the lower bounds calculated using the series coupling scheme of the aggregate model. Although E3 lies close to the lower bound at low λ, it follows the upper bound calculated according to the parallel coupling scheme at λ > 3. The elastic moduli of the composites have similar draw ratio dependences as those of the LCP. The strong increase in E3 with increasing λ arises from the higher aspect ratio of the LCP domains in the composites and the improved molecular orientation within the domains. The reinforcement effect on the other moduli is much weaker, with E1 and C44 of the composites only 5 to 30% higher than those of polycarbonate at λ = 15. Since C66 of the LCP decreases to a value below that of polycarbonate at λ > 2, there is a positive reinforcement effect at low λ but a negative effect at high λ.

A study on the ternary blends of polyphenylenesulfide, polysulfone, and liquid crystalline polyesteramide

AbstractTernary blends of poly(p‐phenylenesulfide) (PPS), thermotropic liquid crystalline polyesteramide (LCP), and polysulfone (PSF) were investigated in terms of processing characteristics, blend morphology, and physical properties. In the incompatible PPS/LCP blends, LCP imparted a nucleating effect to the crystallization of PPS. Up to 10wt% LCP content, the tensile properties of PPS/LCP blends were enhanced with increasing LCP content, but they deteriorated if the LCP content exceeded 20wt%. Addition of a third component, PSF, to the 90/10 PPS/LCP blend promoted development of rodlike or threadlike fibrillar structure and orientation of the deformed LCP domains, which led to improvement of tensile strength up to 20%.

Effects of annealing on the structure formation in the bulk state of thermotropic liquid crystalline polyesteramides with bulky side groups

The isothermal crystallization kinetics of thermotropic liquid crystalline polyesteramides with a phenylhydroquinone derivative was studied by differential scanning calorimetry. The lack of well developed 3-dimensional order, which was evidenced by polarized optical microscopy and thermal analysis, indicated a frozen-in liquid crystalline structure rather than a crystal structure. The crystallization process could be well described by the Avrami equation and it turned out to be a slow process with a low value of Avrami exponent. The transformation of imperfect packing into the ordered molecular packing during the annealing was successfully detected by spin-spin relaxation time ( T 2) measurement.

Liquid crystalline polyesteramides containing crown ether units in the mesogenes

Main chain liquid crystalline polyesteramides containing dibenzo-[18]-crown-6 moieties have been synthesized. Shown by polarisation microscopy and x-ray investigations, these polymers tend to form a mesophase with a layered structure,e.g. smectic A or smectic C type.

Lyotropic liquid crystalline phase of polyesteramides with different ratio of amide to ester groups in a main chain

Various lyotropic liquid crystalline polyesteramides were prepared from 1,3-bis(4-aminobenzoyloxy)benzene, p-phenylene diamine, and terephthalic acid by changing the ratio of amide to ester groups and were observed by using a cross polarized light microscope. The range of liquid crystalline phase becomes wider with increasing the portion of amide groups in a main chain because the chain rigidity becomes higher and the polymer-solvent interaction stronger. In the case of polyesteramides with flexible spacers, the polymer with one p-phenylene group between two ester groups does not form an anisotropic phase but the polymer with the same group between amide groups shows an anisotropy.

Slit die flow measurements of a liquid crystalline polyesteramide and its blends with polyarylate

AbstractA commercial thermotropic polyesteramide and its blends with polyarylate are the object of a slit die flow rheological study. The measurements are carried out at 280°C, a temperature slightly above the melting temperature of the thermotropic, covering a shear rate range 10−1 s−1 to 102s−1. Except in the case of the thermotropic polymer, the pressure profiles are upward parabolic which is attributed to the dependence of the viscosity on pressure. The most striking result is the observed downward curvature in pressure profiles obtained for the liquid crystalline polyesteramide: no explanation is given for this phenomenon, for the present. The elasticity of the polymer melts is expressed in terms of the exit pressure and the extrudate swell. The thermotropic polyesteramide presents negative values of both parameters (e.g. samples shrink instead of swell). Viscosity and elasticity present negative deviation from linearity when plotted against composition; this reduction in the rheological functions, caused by the addition of liquid crystal, is more pronounced at high shear rates.