Polyesters acid chloride reaction

Acid chlorides are generally more reactive than the parent acids, so polyester formation via reaction 5 in Table 5.3 can be carried out in solution and at lower temperatures, in contrast with the bulk reactions of the melt as described above. Again, the by-product molecules must be eliminated either by distillation or precipitation. The method of interfacial condensation, described in the next section, can be applied to this type of reaction. 

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

As a dibasic acid, malic acid forms the usual salts, esters, amides, and acyl chlorides. Monoesters can be prepared easily by refluxing malic acid, an alcohol, and boron trifluoride as a catalyst (9). With polyhydric alcohols and polycarboxyUc aromatic acids, malic acid yields alkyd polyester resins (10) (see Alcohols, polyhydric Alkyd resins). Complete esterification results from the reaction of the diester of maUc acid with an acid chloride, eg, acetyl or stearoyl chloride (11). 

When an amine reacts with an acid chloride, an amide is formed. What would happen, though, if a diamine and a diacid chloride were allowed to react Each partner could form two amide bonds, linking more and more molecules together until a giant polyamide resulted. In the same way, reaction of a diol with a diacid would lead to a polyester. 

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). 

The reaction between acid chlorides and aliphatic alcohols or phenolic compounds commonly takes place at low to moderate temperature (—10 to 100°C) in solution or by interfacial or dispersion polymerization techniques. It has been widely applied to polyester synthesis. Reviews and books are available on the polymerization techniques as well as on the chemistry of this reaction.2,207 294... 

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... 

Those polyester FBAs containing a benzoxazole group are usually prepared from the appropriate o-aminophenol and carboxylic acid (11.45 Y = OH) or one of its derivatives, as shown in Scheme 11.10. The reaction proceeds via an intermediate amide and it can be advantageous to start from an acid derivative such as the acid chloride (11.45 Y = Cl) or ester (11.45 Y = OEt), which are both more effective acylating agents. The preparation of compound 11.36, shown in Scheme 11.11, illustrates this process, but the optimum conditions for ring closure vary considerably from one structure to another. The article by Gold contains a valuable and detailed summary [4]. 

It seems reasonable that polyester cyclics could be prepared by an extension of the /wendo-high-dilution [17] chemistry used for the preparation of cyclic carbonate oligomers [18, 19] however, such proved not to be the case. Brunelle et al. showed that the reaction of terephthaloyl chloride (TPC) with diols such as 1,4-butanediol did not occur quickly enough to prevent concentration of acid chlorides from building up during condensation [14]. Even slow addition of equimolar amounts of TPC and butanediol to an amine base (triethylamine, pyridine or dimethylaminopyridine) under anhydrous conditions did not form cyclic oligomers. (The products were identified by comparison to authentic materials isolated from commercial PBT by the method of Wick and Zeitler [9].)... 

Many of the polymers that are produced by the usual high-temperature reactions could be produced at lower temperatures by using the faster Schotten Baumann reactions of acid chlorides. Thus polyesters and polyamides could he produced by replacing the diacid or di-eser reactant by the corresponding diacyl chloride... 

In principle, the attainment of chemical equilibrium can be accelerated by catalysts however, in contrast to polyester formation, catalysts are not absolutely essential in the above-mentioned polycondensations. The first two types of reactions are generally carried out in the melt solution polycondensations at higher temperature, e.g., in xylenol or 4-fert-butylphenol are of significance only in a few cases on account of the poor solubility of polyamides. On the other hand, polycondensation of diamines with dicarboxylic acid chlorides can be carried out either in solution at low temperature or as interfacial condensation (see Sect. 4.1.2.3). 

As in the preparation of polyesters, also in the preparation of polyamides, the reaction temperature can be considerably reduced by using derivatives of dicarbo-xylic acids instead of the free acids. Especially advantageous in this connection are the dicarboxylic acid chlorides which react with diamines at room temperature by the Schotten-Baumann reaction this polycondensation can be carried out in solution as well as by a special procedure known as interfacial polycondensation (see Examples 4-11 and 4-12). 

The synthetic chemistry for polyesters is briefly reviewed and then is illustrated with a laboratory experiment for preparing poly(l,4-butylene isophthalate) involving the reaction of an acid chloride and a diol. 

Polyethers and polyesters having methoxybenzalazine units with various alkylene groups (C4, C6 and Cg) in the main chain were synthesized from vanillin (7,8). The condensation reaction of 4,4 -alkylenedioxybis (3-methoxybenzaldehyde) [VI] with hydrazine monohydrate was applied to the synthesis of polyethers [VII] (Mn, 7.4 x 103 for C4, 7.3 x 103 for C6 and 4.1 x 103 for Cg derivatives), as shown in Scheme 3. Polyesters [IX] (77jnh, 0.35 dl/g for C4, 0.38 dl/g for C6 and 0.43 dl/g for Cg derivatives) were synthesized from 4,4 -dihydroxy-3,3 -dimethoxybenzalazine [VIII] and di-carboxylic acid chlorides by conventional low temperature solution polycondensation, as shown in Scheme 4. 

Figure 5.21. Reaction schemes for the most common types of step-growth polymerization. Shown are (a/c) polyester formation, (b/d) polyamide formation, (e) polyamide formation through reaction of an acid chloride with a diamine, (f) transesterification involving a carboxylic acid ester and an alcohol, (g) polybenzimidazole formation through condensation of a dicarboxyhc add and aromatic tetramines, and (h) polyimide formation from the reaction of dianhydrides and diamines.

Some of the most familiar reactions falling into the polycondensation class are those leading to polyamides derived from dicarboxylic acids and diamines, polyesters from glycols and dicarboxylic acids, polyurethanes from polyols and polyisocyanates, and polyureas from diamines and diisocyanates. Similar polymer formations utilizing bifunctional acid chlorides with polyols or polyamines also fall into this class. The condensations of aldehydes or ketones with a variety of active hydrogen compounds such as phenols and diamines are in this group. Some of the less familar polycondensation reactions include the formation of polyethers from bifunctional halogen compounds and the sodium salts of bis-phenols, and the addition of bis-thiols to diolefins under certain conditions. 

Two different synthetic routes to polyesters are through the reaction of glycols or other polyfunctional hydroxy-compounds emd anhydrides such as phthalic anhydride, and by the reaction of acid chlorides with glycols or bisphenols. These two reactions may be regarded as irreversible. In the case of polyester-forming reactions that involve the use of acid chlorides (Section 5.7), the reaction proceeds better when the hydrochloric acid produced in the polycondensation is effectively removed, by neutralization, for example. 

The most important method used in the preparation of polyamides is direct amidation, usually through the intermediate formation of a salt of the diamine and dicarboxylic acid, but without it in the case of aminoacids or for pairs of monomers that do not readily form a salt. Esters can react with diamines to form polyamides with liberation of alcohol or phenol. Diamines can be reacted with diamides yielding polyamides and freeing ammonia. Polyamides have been prepared by acidolysis of acyl derivatives of diamines (compare Section 5.4 for acidolysis in polyester preparation). Bis-anhydrides react with diamines to form polyamides and, if reacted further, polyimides. The low-temperature reaction of acid chlorides with diamines has been used, interfacially or as a solution technique, to prepare certain polyamides (compare Section 5.7 for related reactions in polyester synthesis). 

Interfacial reactions have been employed using the reactions of dicar-boxylic acid chlorides with diamines to form polyamides, with hydrazine and hydrazides to form polyhydrazides disulphonyl halides have been used to prepare polysulphonamides diisocyanates and glycols have been used to prepare polyurethanes interfacially (Section 7) and diisocyanates and diamines have been reacted interfacially to form polyureas [6] (Section 8). Polyesters prepared by this technique were discussed in Section 5.7. 

For use in plastics, this might require chain extension with diisocyanates, bisoxazolines, carbodiimides, bis(an-hydrides), and such. One use of the oligomers would be to form polyurethanes by reaction with isocyanates. The use of acid chlorides can be avoided if the polymers are made by ester exchange or made enzymatically, with compounds such as divinyl adipate. Poly(butylene sebacate) with a molecular weight of 46,400 has been made has been made from bis(2,2,2-trifluoroethyl)sebacate and 1,4-butane diol.150 One polyester with a molecular weight of 24,000 has been made by ester exchange from isosorbide and a... 

Work on improving the thermal resistance and particularly the resistance to carbonization (short circuiting of layers of enameled wires under the influence of temperature) via special glycols led to diphenols [29,30]. Diphenols are not reactive under the conditions of a normal poly(ester-imide) synthesis. In synthesis the lower aliphatic diesters of diphenols were used [29-32]. The use of acid chlorides in the polyester reaction with aromatic OH-groups was also protected by patents [33-35] but it seems unlikely that this reaction was performed on the production scale. 

Reaction of Acid Chlorides. Polyesters can be formed by the reaction of diacid chlorides with diols ... 

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