Glycols, aliphatic, polyesters

Aliphatic-aromatic liquid-crystalline polymers, synthesis, 16-17 Aliphatic glycol polyesters experimental procedures, 17-18 properties, 17... 

Polyesters of 4,4 -Biphenyldicarboxylic Acid and Aliphatic Glycols for High-Performance... 

Thermotropic liquid crystalline polyesters (ICP s) were prepared from the dimethyl ester of 4,4 -bi-pheriyldicarboxylic acid (BDA) and aliphatic glycols containing 2 to 10 methylene units and ccnpared with similar trans-4,41 -stilbenedicarboxyl ic acid (SDA)... 

Unsaturated polyesters obtained by polycondensation of saturated and unsaturated acids, anhydrides and aliphatic glycols are used as coating resins and as matrices in glass-reiforced products. 

Among the high molecular weight aliphatic-aromatic polyesters, the highest commercial volume material is poly(ethylene terephthalate). Most of it is prepared from dimethylene terephtha-late and ethylene glycol by a transesterification reaction ... 

Due to the hydrophobic nature of the cyclohexylene unit, the polyesters based on 1,4-CHDM are more hydrolytically stable than those others made from aliphatic glycols as neopentyl glycol or 2-butyl-2-ethy 1-1,3-propanediol (115). The effect of annealing and aging in water on the properties of amorphous PE CjuT were studied by Golovoy et al. (116). The annealing treatment induced... 

Aliphatic polyesters are generally sensitive to hydrolysis and are biodegradable (Gross and Bhanu, 2002). They are formed by the polycondensation reaction of an aliphatic glycol with an aliphatic dicarboxylic acid. Among the aliphatic polyesters there is a family of polymers, the poly(a-hydroxy acids) such as polyglycolic acid (PGA), polylactic acid (PLA), and some of their copolymers, which have been used in a number of clinical applications sutures, plates and fixtures for fracture fixation devices and scaffolds for cell transplantation. 

Polyesters are the most important class of synthetic fibers. In general, polyesters are produced by an esterification reaction of a diol and a diacid. Carothers (1930) was the first to try to synthesize a polyester fiber by reacting an aliphatic diacid with a diol. The polymers were not suitable because of their low melting points. However, he was successful in preparing the first synthetic fiber (nylon 66). In 1946, Whinfield and Dickson prepared the first polyester polymer by using terephthalic acid (an aromatic diacid) and ethylene glycol. 

Hie most representative member of this class of polyesters is the low-molar-mass (M 1000-3000) hydroxy-terminated aliphatic poly(2,2/-oxydiethylene adipate) obtained by esterification between adipic acid and diethylene glycol. This oligomer is used as a macromonomer in the synthesis of polyurethane elastomers and flexible foams by reaction with diisocyanates (see Chapter 5). Hydroxy-terminated poly(f -caprolactonc) and copolyesters of various diols or polyols and diacids, such as o-phthalic acid or hydroxy acids, broaden the range of properties and applications of polyester polyols. 

The semicrystalline polyesters of the terephthalate and naphthalate family are resistant to a wide range of chemicals at room temperature, including water, alcohols, ketones, ethers, glycols, chlorinated solvents, aliphatic hydrocarbons, and oils. They are slowly hydrolyzed in boiling water and rapidly degraded in strongly basic or acidic medium. 

Common biodegradable polymers for medical devices are constructed from synthetic linear aliphatic polyesters. One material commonly used for internal sutures is poly(glycolic acid) (PGA). PGA is synthesized from the dimer of glycolic acid (Fig. 13.1.l). 1... 

Several novel biodegradable polyesters of different compositions have been developed during the last decade, e.g., an aliphatic copolymer of various glycols and dicarboxylic acids (Bionolle) or copolymers of aliphatic diols and aromatic monomers [119-121]. 

Biodegradation of the aliphatic polyesters occurs by bulk erosion. The lactide/gly-colide polymer chains are cleaved by random nonenzymatic hydrolysis to the monomeric lactic and glycolic acids and are eliminated from the body through the Krebs cycle, primarily as carbon dioxide and in urine. 

---