Polyesters synthesis from diols

Fig. 1-30. Polyester synthesis from the carbonylative polycondensation of aromatic dibromides and diols (adapted from [237]).

Polyesters are formed by typical condensation reactions involving the elimination of water and an example of polyester synthesis from a diol and a diacid is reported as follows ... 

The carboxy-hydroxy reaction (direct esterification) is the most straightforward method of polyester synthesis. It was first reported in the 1930s by Carothers10 12 and is still a very widely used method for the synthesis of polyesters from diacids and diols (Scheme 2.12) or from hydroxy acids (Scheme 2.13). Direct... 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

The common condensation polymers and the reactions by which they are formed are shown in Table 1-1. It should be noted from Table 1-1 that for many of the condensation polymers there are different combinations of reactants that can be employed for their synthesis. Thus polyamides can be synthesized by the reactions of diamines with diacids or diacyl chlorides and by the self-condensation of amino acids. Similarly, polyesters can be synthesized from diols by esterification with diacids or ester interchange with diesters. 

Completely aliphatic polyesters, made from aliphatic diacid and aliphatic diol components), are not of major industrial importance because of their low melting temperatures and poor hydrolytic stability. (Low-molecular-weight aliphatic polyesters are used as plasticizers and prepolymer reactants in the synthesis of polyurethanes see Secs. 2-12e, 2-13c-2). 

Several review articles on biodegradable polymers and polyesters have appeared in the literature [12-22]. Extensive studies have been carried out by Al-bertsson and coworkers developing biodegradable polymers such as polyesters, polyanhydrides, polycarbonates, etc., and relating the structure and properties of aliphatic polyesters prepared by ROP and polycondensation techniques. In the present paper, the current status of aliphatic polyesters and copolyesters (block, random, and star-shaped), their synthesis and characterization, properties, degradation, and applications are described. Emphasis is placed primarily on aliphatic polyesters derived by condensation of diols with dicarboxylic acids (or their derivatives) or by the ROP of cyclic monoesters. Polyesters derived from cyclic diesters or microbial polyesters are beyond the scope of this review. 

A saturated poly(ester-imide) is made by modifying linear or branched polyesters with imide-containing structures (Fig. 3). The synthesis, which is described below in more detail, starts from polyester components like diols and triols (e.g. glycol and THEIC), diacids or reactive diacid derivatives, like terephthalic acid... 

Okumara et al. [10] were the first to attempt the enzyme-catalyzed synthesis of oligoesters from a reaction between dicarboxylic acids and diols. Gutman et al. [11] reported the first study on polyester synthesis by enzyme-catalyzed polymerization of A-B type monomers. Two independent groups in 1993 [12, 13] were first to report enzyme-catalyzed ring-opening polymerization (ROP). Their studies focused on 7- and 6-membered unsubstituted cyclic esters, e-caprolactone (e-CL) and 8-valerolactone (8-VL), respectively. 

Another recent study on polyester synthesis through thiol-ene reactions for preparation of monomers from fatty-acid derivatives was described by Pang and co-workers [16]. Authors adopted the same approach for preparing aliphatic diols and diester from 10-undecen-l-ol, methyl 10-undecenoate and thiols. In parallel, they prepared aromatic diesters from methyl vanillate and a series of thermoplastic polyesters were synthesised by polycondensation of the diols and diesters using conventional transesterification methods. These materials were obtained with Mn values of 12-27 kDa and T values of -13 to 13 °C. 

Aliphatic polyesters and polyesters formed from aromatic diacids and aliphatic diols eg, poly(ethylene terephthalate) and poly(butylene terephthalate) (3) cannot decompose by reversion of the polymerization, because the water, or alcohol, eliminated in the synthesis is no longer available. They initially decompose by /3-C—H transfer reactions via a six-membered transition state ... 

This is the preferred method for the synthesis of both, aliphatic and aromatic polyesters derived from CHDM. The reaction is usually accomplished in two steps. The first step is carried out under a pressure which depends on the diacid or the dimethyl ester derivative used for the synthesis. Usually an excess of diols to diacid (1.2-2.2 1) is employed so a mixture of short oligomers is produced. In the second polycondensation step, which is carried out at higher temperatures and under vacuum, the oligomers react to generate the polymer and the excess of diol is removed. If the resulting polyester is crystalline it may be subjected to solid state postpolycondensation (SSP) in order to increase the molecular weight. 

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