Polyesters, liquid crystalline characterization

James DF and Walters K, "A Critical Appraisal of Available Methods for the Measurement of Extensional Properties of Mobile Systems" in Collyer AA (Ed), "Techniques in Rheological Measurement", Chapman Hall, London, 1993. Jin S, "Synthesis and Characterization of Side-Chain Liquid Crystalline Polyesters and Polyurethanes", PhD Thesis, Delft, 1995. 

High resolution solid-state NMR spectroscopy is also a very powerful method for characterizing the solid structure and the local motion of different solid polymers. We recently characterized the crystalline-noncrystalline structure for different crystalline and liquid crystalline polymers, such as polyolefins [7-12], polyesters [13-15], polyether [16], polyurethanes [17, 18] and polysaccharides, including cellulose [19-29], amylose [30, 31] and dextran [32]. On the basis of these analytical methods, we also investigated the intra- and intermolecular hydrogen bonds of PVA in both crystalline and noncrystalline regions as well as in the frozen solution state. In this chapter. 

Thermotropic polyester backbone chemistry is characterized by a high degree of aromaticity, planarity, and linearity in the chain backbone. Most common moieties are p-phenylene, 1,4-biphenyl, and 2,6-naphthalyl moieties linked by ester or amide linkages. Polymers that form liquid crystal phases in the melt are thermotropic, whereas those that form liquid crystalline phases in solution are lyotropic. The all-aromatic polyester homopolymers tend to be intractable, decomposing at temperatures well below their melting points and insoluble in most... 

The thermal reaction of cobalt polymers 4.28 with isocyanates at 120 °C leads to 2-pyridone-containing polymers such as 4.30 [70]. Well-characterized, yellow polyesters 4.31 containing skeletal (cyclobutadiene)cobalt moieties in the main chain have been prepared by interfacial polycondensation approaches [73]. The use of solubilizing alkoxy substituents R afforded materials with Mn = 5,400-16,300 (PDI = 1.3-1.8). Analogous materials to 4.31 with a 1,3-disposition of the main-chain substituents on the cyclobutadiene ligands have also been studied [73, 74]. Thermotropic liquid crystallinity was detected by polarizing microscopy, with, in some cases, mesophases stable over the temperature range from about 110 to >250°C. 

Synthesis and Characterization of Block Copolymers Containing Poly(aryl ester ketone) and Liquid Crystalline Polyester Segments. Chem. J. Chin. Univ, 26(3), 589-591. 

This book covers a wide range of topics and addresses different disciplines in the field. The chapters are arranged as a learning scheme for the professional, from basic science to applied engineering. The first few chapters summarize the syntheses of various polyester, polyester-amide, and polyimide liquid crystalline polymers. The science and origins of liquid crystal formation are revealed. Next, we introduce the characterizations of these materials by their different chemical and physical aspects. To help the reader, the principles of material characterizations are also discussed. 

Characterization of the copolyesters were carried out using differential scanning calorimeter. A typical uncatalyzed runs (Figure 5) is shown. The plot reveal that the polyesters are liquid crystalline in nature. 

The commercial polymers used in the study are characterized in Table 1. The polypropylenes PP1-PP5 were homopolymers exhibiting different melt viscosities (see Fig. 1) supplied by Neste Chemicals. Liquid-crystalline polymer 1 (LCPl) (Vectra A950 by Hoechst Celanese) is a totally aromatic polyester-type thermotropic main-chain LCP copolymer based on p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA). Liquid-crystalline polymer 2 (LCP2) (Rodrun LC-3000 by Unitika Ltd) is a more flexible thermotropic main-chain LCP copolyester consisting of 60%... 

The previous paper in this series described the preparation and properties of highly aromatic polyesters that have turbid melts, have melt viscosities highly dependent upon composition and shear rate, and that give unusually anisotropic molded articles. Because these unusual properties are reminiscent of the behavior of nonpolymeric nematic liquid crystalline materials, further work has been done to synthesize and characterize polymers containing other moieties known to lead to liquid crystallinity in nonpolymeric materials. The copolyesters produced were derived by the acidolysis reaction previously described from poly-(ethylene terephthalate) (PET) and a variety of dicarboxylic acids and acetylated difunctional phenols. Some of the copolymer compositions were varied to determine the limits of composition that give the turbid melts characteristic of liquid crystallinity, but which can be melted before decomposition. This paper describes the preparation and the physical and magnetic properties of these polymers. 

Malik TM, Carreau PJ, Qiapleau N (1989) Qiaracterization of liquid crystalline polyester polycarbonate blends. Polym Eng Sci 29(9) 600-608 Manson JAE, Seferis JC (1992) Process simulated laminate (PSL) a methodology to internal stress characterization in advanced composite materials. J Compos Mater 26(3) 405 31 Meng YZ, Tjong SC, Hay AS (1998) Morphology, rheological and thermal properties of the melt blends of poly (phthalazinone ether ketone sulfone) with liquid crystalline copolyester. Polymer 39(10) 1845-1850... 

The thermotropic group consists of a crystalline liquid formed during cooling of a dry melt (similar to the processing of thermoplastics)—the first having been the aromatic polyesters (1972). When a disordered melt cools in a region of proper transition temperature (Tj), a liquid crystal phase (mesophase) is formed. It is characterized by high order (anisotropic) that creates turbidity. 

Polymers are dissolved in their solvents and precipitated by their nonsolvents. The general term solvent is, however often nsed for any liquid so that a nonsolvent for given polymer is also a sort of solvent . As a rule, polymers dissolve in liquids that exhibit certain similarity with macromolecules, for example, a likeness in polarity. Polarities of polymers and solvents are characterized by solubility parameters, 5, values of which can be foimd for example in Polymer Handbook (compare the Recommended Reading). Crystalline polymers are often soluble only above their melting point. Typical examples are polyolefins. Some solvents are able to dismpt crystalline stracture of polymers and dissolve them at ambient temperature (compare sections 11.6.2 and 11.7.3.2). The practically important example is hexalluoro isopropanol, HP IP, which dissolves several polar crystalline polymers, for example aromatic polyesters. Already presence of 2% of HFIP enables to keep the latter polymers molecularly dispersed in the low polarity liquid, chloroform. 

---