Aromatic polyester synthesis

Similarly, the addition of low quantities of vinyl or polyvinylthiazoles in the synthesis of aromatic polyesters increases the rate of polymerization (315). 

Transesterifications, also termed ester exchange or ester interchange reactions, include hydroxy-ester, carboxy-ester, and ester-ester reactions. Hydroxy-ester reaction is the most important one and is used for many aromatic-aliphatic and wholly aromatic polyester syntheses. Carboxy-ester interchange is restricted to the synthesis of wholly aromatic polyesters while the ester-ester route is rarely used for polyester preparation due to slow kinetics. All these reactions may take place in comparable experimental conditions and can be catalyzed by similar classes of compounds. 

The use of silylated monomers is an interesting alternative method of aromatic polyester synthesis since the silylated gaseous by-products cannot participate in the reverse reaction, shifting polyesterification toward polymer formation. Reactions between silyl esters and acetates (Scheme 2.23) and reactions between silyl ethers and acid chlorides (Scheme 2.24) have been applied to the synthesis of linear265-267 and hyperbranched wholly aromatic polyesters202,268 269 (see Section 2.4.5.2.2). 

Aliphatic-aromatic copoly imides, 268 Aliphatic-aromatic polyesters, 18, 19 Aliphatic degradable polyesters, 41 Aliphatic diacids, polyamide synthesis from, 183-184... 

Hyperbranched aromatic polyesters, synthesis of, 116-118 Hyperbranched aromatic polymers, 286 Hyperbranched polyamine, synthesis of, 519-520... 

Phthalazinone, 355 synthesis of, 356 Phthalic anhydride, 101 Phthalic anhydride-glycerol reaction, 19 Physical properties. See also Barrier properties Dielectric properties Mechanical properties Molecular weight Optical properties Structure-property relationships Thermal properties of aliphatic polyesters, 40-44 of aromatic-aliphatic polyesters, 44-47 of aromatic polyesters, 47-53 of aromatic polymers, 273-274 of epoxy-phenol networks, 413-416 molecular weight and, 3 of PBT, PEN, and PTT, 44-46 of polyester-ether thermoplastic elastomers, 54 of polyesters, 32-60 of polyimides, 273-287 of polymers, 3... 

Weathering tests, 245 Wholly aromatic liquid crystalline polyesters, degradation of, 38 Wholly aromatic polyamides, 136-137, 139 synthesis of, 184-189 Wholly aromatic polyesters, 25-26, 32 copolymerization and, 35 synthesis of, 71-72... 

Considerable attention has been paid to aromatic hyperbranched polyesters synthesized from monomers derived from 3,5-dihydroxybenzoic acid (DBA). The thermal stability of DBA is not good enough to allow direct esterification of DBA, and therefore chemical modifications are necessary. Some aromatic monomers used for the synthesis of hyperbranched aromatic polyesters are presented in Fig. 6. 

The highest purity of monomers and exact control of the reaction conditions are necessary for the synthesis of aromatic polyesters. 

Kallitsis, J.K., Kakahli, F. and Gravalos, K.G. (1994) Synthesis and characterization of soluble aromatic polyesters containing oligophenyl moieties in the main chain. Macromolecules, 27, 4509-15. 

Some industrially important polymeric materials can be prepared using the basic strategies discussed earlier. A representative example can be found in the synthesis of polyesters using the carbonylative polycondensation of aromatic dibromides and diols (Fig. 1-30) [237]. The underlying principle is no different from the fundamentals of carbonylative coupling presented earlier in Section 1.5.1.3. Replacement of the diols with hydrazides 86 similarly yields poly(acylhydrazide)s 87 [238]. The catalytic... 

The aromatic polyesters such as poly(ethylene terephthalate) (PET) were commercialized from about 1946 as fibres, but, because of the high processing temperatures, it was only some 20 years later that they appeared as engineering thermoplastics. The dominance of PET in beverage containers ensures the importance of the synthesis, processing and recycling of PET. Polyesterification is a suitable stepwise reaction to illustrate the principles of this industrially important polymerization. Applications in reactive processing will then be considered. 

The chemical participation of lignin macromonomers in polymerization or copolymerization reactions has been focussed mostly on the reactivity of both types of OH groups, and hence in the synthesis of polyesters, polyurethanes and polyethers, although some research has also dealt with their intervention through the unsubstituted aromatic sites in different formaldehyde-based resins in partial replacement of phenol [58, 59]. 

Uyama, H., Shigeru, Y., and Kobayashi, S. (1999) Enzymatic synthesis of aromatic polyesters by lipase-catalyzed polymerization of dicarboxylic acid divinyl esters and glycols. Polym. J., 31 (4), 380-383. 

Polyester polyols with equivalent weight of 167, functionality of 2 OH groups/mol, hydroxyl number of 310-350 mg KOH/g and viscosity of 1,300-3,000 mPa-s at 25 °C, are used in thermal insulation of appliances. The initial ratio between DEG and PET used in synthesis, followed by the utilisation of one of the previously mentioned procedures avoids solidification (section 16.2, a-e), and means that a large range of aromatic polyester polyols, having various hydroxyl numbers, functionalities and aromaticity can be obtained. 

Although aromatic polyesters had been successfully synthesized from the reaction of ethylene glycol with various aromatic diacids (almost always terephthalic acid or its ester), commercialization of polyester synthesis awaited an inexpensive source of aromatic diacids. In 1953 an inexpensive process for the separation of the various xylene isomers by crystallization was discovered. The availability of inexpensive xylene isomers enabled the formation of terephthalic acid through the air oxidation of the p-xylene isomer. Du Pont, in 1953, produced polyester fibers from melt spinning, but it was not until the 1970s that these polyester fibers became commercially available. 

Throughout this chapter, the examples of polymerizations in compressed CO2 have been primarily for chain growth polymerization processes. However, step-growth methods represent an area of new interest for SCFs. Initial experiments in this area include the synthesis of aromatic polyesters such as poly(ethylene terephthalate) (PET) in SCCO2 as illustrated in Scheme 4.5-9 [144]. An advan-... 

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