Polyester, aliphatic unsaturated

Although low-molar-mass aliphatic polyesters and unsaturated polyesters can be synthesized without added catalyst (see Sections 2.4.1.1.1 and 2.4.2.1), the presence of a catalyst is generally required for the preparation of high-molar-mass polyesters. Strong acids are very efficient polyesterification catalysts but also catalyze a number of side reactions at elevated temperature (>160°C), leading to polymers of inferior quality. Acid catalysts are, therefore, not much used. An exception is the bulk synthesis of hyperbranched polyesters reported in Section 2.4.5.1, which is carried out at moderate temperature (140°C) under vacuum in the presence of p-toluene sulfonic acid catalyst. The use of strongly acidic oil-soluble catalysts has also been reported for the low-temperature synthesis of polyester oligomers in water-in-oil emulsions.216... 

Linear unsaturated polyesters contain aliphatic unsaturation that can result in subsequent cross-linking. The first such product was prepared in 1946 by the condensation of maleic anhydride... 

It is known that increased char yield is usually associated with improved flammability behavior ( 1). This can be understood if one considers that the volatile flammable products can only diffuse with difficulty through the char, and that the thermal conductivity of a porous char layer is relatively poor (2). The structure of the polymer can contribute to the amount of char formed based on the character of the functional groups present and the nature of the backbone (2,3). Ritchie ( ) found that for a series of unsaturated polyesters and their copolymers, the temperatures at which carbon dioxide is eliminated was in the range of 280 to 345°C depending on the structure of the polyester. Aliphatic polyesters and their copolymers have less thermal... 

CLASS Thermoset polymers (mixtures of polyester prejxjlymers with aliphatic unsaturation and a vinyl monomer)... 

The materials in this group are linear copolyesters. One of the dicarboxylic acids is an aliphatic unsaturated diacid. The unsaturation is introduced into the polymer backbone for the purpose of subsequent crosslinking. Unsaturated polyester technology was developed for use in glass fiber laminates, thermosetting molding compositions, casting resins, and solventless lacquers. 

Zhang and co-workers developed unique crosslinkable unsaturated polyesters by a one-pot lipase-catalysed oxidation followed by copolymerisation of crude linoleic acid, glycerol and l,18-ds-9-octanedecenedioic acid [81]. In a similar approach, Roumanet and co-workers prepared aliphatic unsaturated polyesters derived from l,18-(Z)-octadec-9-enedioic acid (a derivative of fatty acids from sunflower oil) and aliphatic diols of different molecular weight [82]. The double bonds of the ensuing polyester backbones were then epoxidised and photocrosslinked, yielding transparent and homogeneous crosslinked films with high hydrophobicity. 

Figure 8.10 Typical structure of substituted polyester from substituted hydroquinone and aliphatic unsaturated dicarboxylic acid.

The photo-oxidation of aliphatic unsaturated polyesters such as poly(l,2-maleate) (4.46) [2188] and poly(propylene-l,2-maleate) (4.47) [1099, 1357, 1474, 1475, 1814] is accompanied by extensive chain scission, crosslinking and yellowing. 

The polymers making up this first group of polyesters are linear polyesters containing aliphatic unsaturation which provides sites for subsequent cross-linking. A polymer of this type first became available in the USA in 1946 the polymer was prepared from diethylene glycol and maleic anhydride and... 

In the enzyme-catalyzed synthesis of aliphatic, unsaturated and semi-aromatic polyesters from diesters and diols in organic solvents, macrocyclic rings are formed concurrently with the linear chains, with a relative proportion heavily dependent on both the monomer structure and the initial concentration of all... 

Epoxide-containing polyesters were enzymatically synthesized via two routes using unsaturated fatty acids as starting substrate (Scheme 11)." Lipase catalysis was used for both polycondensation and epoxidation of unsaturated fatty acid group. One route was synthesis of aliphatic polyesters containing an... 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

Unsaturated polyesters are prepared through a classical esterification process. Typically, a dihydroxy compound, or mixtures of dihydroxy compounds, are treated with maleic anhydride and/or together with other dicarboxylic acids such as aromatic or aliphatic dicarboxylic acids under elevated temperature to remove the water produced during esterification process. Although various catalysts will catalyze this esterification reaction, there is enough carboxylic acid in the mixture so that it is not necessary to add extra catalyst. 

The purpose of this review is to report on the recent developments in the macromolecular engineering of aliphatic polyesters. First, the possibilities offered by the living (co)polymerization of (di)lactones will be reviewed. The second part is devoted to the synthesis of block and graft copolymers, combining the living coordination ROP of (di)lactones with other living/controlled polymerization mechanisms of other cyclic and unsaturated comonomers. Finally, several examples of novel types of materials prepared by this macromolecular engineering will be presented. 

The fungus assimilated various polyesters. In general, assimilation of aliphatic polyesters by the fungus was better the greater the number of carbon atoms between the ester bonds. Polyesters with side chains were generally less assimilated than without side chains. The fungus also assimilated unsaturated aliphatic polyesters, but hardly assimilated alicyclic and aromatic polyesters. 

Lou X, Detrembleur C, Lecomte P, Jerome R (2002) Controlled synthesis and chemical modification of unsaturated aliphatic (co)polyesters based on 6,7-dihydro-2(3H)-oxepinone. J Polym Sci A Polym Chem 40 2286-2297... 

Dihydro-2(3//)-oxepinone undergoes copolymerization with e-caprolactone initiated by aluminium isoprop-oxide at 0 °C as an easy way to produce unsaturated aliphatic polyesters with nonconjugated C=C double bonds in a controlled manner. The homopolymerization of the dihydrooxepinone is, however, not controlled because of fast intramolecular transesterification <2002PSA2286>. 

Maleic anhydride [R1 equals -CH=CH- in Eq. (2.7) cis isomer] is reacted with aliphatic diols to form low molar mass unsaturated polyesters, UP. For molar masses higher than 1000 g/mol, products are diluted with a liquid vinyl monomer, most often styrene. This reactive mixture, generally called unsaturated polyester, UP resin, can be transformed into crosslinked polymers through a free-radical chain polymerization (see Sec. 2.3). 

Unsaturated polyesters can undergo degradation by oxidation of their aliphatic segments, decarboxylation of esters and partial depolymerization of polystyrene chains. 

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