Liquid crystalline polyesters, characteristics

It has also been reported that polymers containing ferrocene units in the main-chain or sidechains may possess liquid crystalline characteristics. " Ferrocene-based liquid crystalline polyesters (3) containing phosphorous groups in their backbones have been reported by Senthd and Kannan. ... 

White JL, Dong L, Han P, Laun HM (2004) Rheological properties and associated structural characteristics of some aromatic polycondensates including liquid-crystalline polyesters and cellulose derivatives. Int Union Pure Appl Chem 76(ll) 2027-2049 Wiberg G, Hillborg H, Gedde UW (1998) Assessment of development and relaxation of orientation in a sheared thermotropic liquid crystalline copolyester. Polym Eng Sci 38 1278-1285 Wilson TS, Baird DG (1992) Transient elongational flow behavior of thermotropic liquid crystalline polymers. J Non-Newt Fluid 44 85-112... 

The Mesogenic Index has been applied to a substantial body of data on polyesters and polyamides drawn from from published literature including 22 systems where the critical concentration for onset of liquid crystallinity has been established with reasonable accuracy (Tables 2 and 3). The characteristic value of the MI at the onset of a liquid crystalline phase is generally found to be remarkably close to 10. When applied to the more limited data available on polyurethanes, polyethers, polycarbonates, the rule holds up well. 

Early studies of the thermal degradation of so-called polyarylates were covered by Neiman [100] and Ehlers and co-workers [101]. Since then, several highly aromatic and specifically liquid crystalline (mesogenic) polyesters have been examined in terms of their anaerobic thermal degradation characteristics. These inclnde homopolymers of hydroxybenzoic acids [102-105] copolymers of hydroxybenzoic acid with hydroxynaphthoic acid [105-108] polymers which are essentially copolymers of hydroxybenzoic acid and alkyene terephthalates [107-118] copolymers of hydroxybenzoic acid with other aromatic polyesters [119-122] phenolic and bisphenolic terephthalates [123-127] poly(oxynaphthoate)s [128] and liquid crystal polyesters (LCP) containing unsaturated acids as part of a copolyester chain [129-131]. 

D. M. Malik et al.. Characteristics of liquid crystalline polymer polyester polycarbonate blends, Polym. Engr. Set, 29 (4) 600 (1989). 

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. 

Polyamides and polyesters containing ruthenimn bipyridine complexes in their structures have been synthesized by Chan and coworkers." " Scheme 14 depicts the synthesis of polymer 64 by reaction of the metal-containing dicarboxylic acid complex 61 and the organic dicarboxylic acid (62) with an aromatic or aliphatic diamine (63). These polymers were thermally stable to temperatures between 320 and 500°C. Many of the polymers exhibited liquid crystalline characteristics. The photoconductivity of this class of polymer increased with increasing metal content." Chan also reported that polybenzo-bw-oxazoles and polybenzo-Z>w-thiazoles that contain ruthenium complexes coordinated to 2,2 bipyridyl units in the backbone... 

Polymers 2a-d were crystalline materials and displayed strong mdting transitions. Polyesters dmved fi-om trans cyclohexane units are (mown to display crystalline and liquid crystalline characteristics (28). These polymers displayed Tg s ranging from -5... 

Benzene is a volatile, colorless, highly flammable liquid that is consumed as a raw material for the manufacture of phenolic and polyester resins, polystyrene plastics, alkylbenzene surfactants, chlorobenzenes, insecticides, and dyes. It is hazardous both for its ignitability and toxicity (exposure to benzene causes blood abnormalities that may develop into leukemia). Naphthalene is the simplest member of a large number of multicychc aromatic hydrocarbons having two or more fused rings. It is a volatile white crystalline solid with a characteristic odor and has been used to make mothballs. The most important of the many chemical derivatives made from naphthalene is phthalic anhydride, from which phthalate ester plasticizers are synthesized. 

It is noteworthy that the products thus prepared possess remarkable physico-chemieal properties (glass transition point mechanical, electrical, and optical characteristics), as evidenced by exeellent transpareney, good moldability, and high resistance to heat, aging, solvents, and weathering. Furthermore, they are eompatible with many polymers, ineluding polyesters, polyearbonates, polyamides, and polyolefins, and find broad application in the manufactme of optical devices, photo disks, circuit boards for crystalline liquids, printed circuit boards, special electrical and electronic devices, and so on. 

Liquid-crystal polymers are a family of materials based on aromatic polyester chemistry. Like other aromatic polymers (such as aramids), the aromatic bonds provide them with enhanced performance over traditional polyester materials. The term liquid crystal implies that they have characteristics of both liquid and solid (e.g., crystalline) materials. (And you have to admit the phrase Liquid Crystal Polymer sounds much better than the term Aromester.)... 

---