Polyesters synthesis from diols with acid

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. 

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... 

To illustrate the recently discovered pathways to functional monomers, Meier and colleagues studied the synthesis of a long-chain diester from a (o-hydroxy fatty acid derived from palmitic acid. The idea was to transform the (0-hydroxyl function into a mesylate, followed by an elimination reaction to prepare the (O-unsaturated fatty acid methyl ester (FAME), which was dimerised by a SM coupling to obtain the desired C30 diester (Scheme 5.5) [14]. This macromonomer was then polymerised with diols and diamines to prepare long-chain polyesters and polyamides (PA) with interesting thermal properties, such as a melting temperature (T ) of 109 °C for the polyester and 166 °C for the PA. 

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. 

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

Esterification and transesterification were used for the synthesis of numerous polymeric stabilizers derived from carboxylic as well as inorganic acids. Systems obtained with poly(alkylene ether)diols contain polyether and polyester links. 

Polycondensation of acid anhydrides (maleic and phthalic anhydrides) with diols (e.g. ethylene glycol) under microwave irradiation conditions has also been described for synthesis of unsaturated polyesters [52]. In addition to the previous procedure, the reaction temperature was increased to 200 °C and a Dean-Stark trap was used to remove water from the reaction mixture (Scheme 14.23). It was found that reaction times for the microwave and conventional procedures were comparable and depended on the rate of removal of water from the reaction system. 

The polycondensation of a diol and the diester of a dicarboxylic acid (e.g., the dimethyl ester) can be carried out in the melt at a considerably lower temperature than for the corresponding reaction of the free acid. Under the influence of acidic or basic catalysts a transesterification occurs with the elimination of the readily volatile alcohol (see Example 4.3). Instead of diesters of carboxylic acids one can also use their dicarboxylic acid chlorides, for example, in the synthesis of high-melting aromatic polyesters from terephthaloyl dichloride and bisphenols. The commercially very important polycarbonates are obtained from bisphenols and phosgene, although the use of diphenyl carbonate as an alternative component is of increasing interest (see Example 4.4). Instead of free acids, cyclic carboxylic... 

---