Polyesters from acid chlorides

Diacyl chlorides react with glycols or other diols such as bisphenols without catalyst, forming polyesters in the presence of an acid acceptor removal of the hydrochloric acid formed is important to the equilibrium 

These reactions can be carried out in the melt [76], in solution using inert solvents, or by interfacial polymerization. 

A4 the higher temperatures used in melt polycondensations it is necessary to remove the liberated hydrogen chloride by bubbling inert gas through the reaction medium. Side reactions are common, and this polymerization method is used only rarely. No major kinetic studies have been made. 

The size of the active portion of the activated complex in the rate-determining step was estimated [77] to be 2 0.1 A, supporting the proposal that the reaction product first exists as a protonated molecule. 

When the polycarbonate of bisphenol A was made interfacially in a non-solvent for the polymer the distribution of molecular weights showed two clear maxima and was unusually broad [40]. This was probably a consequence of the two-step process often employed in the preparation of polycarbonates here, the first step yields low-molecular-weight polymer from phosgene and the aqueous alkaline solution of the aromatic diol, then an accelerator salt and more alkali and phosgene are added in the second step. Polycarbonates prepared in the melt and in solution show the expected essentially statistical distribution of molecular weights [40]. Polycarbonates have also been prepared from bisphenols and bisphenol bischloroformates studies of this reaction in nitrobenzene solution have shown it to be second order [79]. 

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PREPARATION OF POLYESTER CYCLIC OLIGOMERS FROM ACID CHLORIDES... 

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). 

Trinitrochlorobenzene (piciyl chloride) in pyridine-A -mcthylpyrrolidi-none (NMP) solutions were later used for the preparation of polyesters from dicarboxylic acids and diphenols or aliphatic diols,309 but better results have been obtained with sulfonyl chlorides and phosphorus compounds. 

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]. 

Table I. Values of b for polyester-forming systems derived(21 ) from Figure 5 and plots of X b versus (cac + Cbc)-1 according to equations(7). vA(-/v-fractional length of acid chloride residue in the chain of v bonds, (i) cext = cao + cbo- (ii) cext = cac + cbc For explanation of reactants see Figure 5.

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].)... 

In view of the utility of the aromatic polyesters and the demonstrated effectiveness of the aromatic polyphosphonates as flame retardants, the combination of these two polymers was chosen for this study. In addition, this system provided a composition in which both copolymers and polymer blends could be prepared with identical chemical compositions. The polyesters were prepared from resorcinol with an 80/20 m/m ratio of iso-phthaloyl and terephaloyl chlorides while the polyphosphonates were resorcinol phenylphosphonate polymers. Copolymerized phosphorus was incorporated by replacement of a portion of the acid chloride mixture with phenylphosphonic dichloride. 

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. 

Using the much more reactive acid chloride monomer allows polyester production at much lower temperatures than when using the ester, or free acid. Even under ambient conditions it is so vigorous that interfacial polymerization of diluted solutions of the monomers in an appropriate, immiscible solvent pair may be needed to control the rate. However, the high cost of the acid chloride as compared to terephthalic acid or the ester makes this route commercially unattractive. Also with this monomer pair the kinetic treatment and molecular weight distributions will differ from the general cases outlined in Chapter 20. 

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... 

Carboxylic acids, acid chlorides, and acid anhydrides react with alcohols to produce esters, objective 6 (Section 5.5), Exercise 5.36 Polyesters result from the reaction of dicar-boxylic acids and diols. Polyesters are an example of condensation polymers these are produced when monomers react to form a polymer plus a small molecule such as water. Many esters are very fragrant and represent some of nature s most pleasant odors. Because of this characteristic, esters are widely used as flavoring agents. 

Later, Braun et al. reported the synthesis of a broad range of polyesters from isosor-bide/isomannide and acid dichlorides via melt condensation [12], The acid chlorides used include linear C4-C16 alkanoyl, ortho/iso/terephthaloyl, and 1,8- and 2,6-naphthalenoyl. Relatively high aliphatic polyesters were obtained, with up to 60 000 (GPC) for poly(isosorbide sebacate). Contrary to the aliphatic polyesters, the semi aromatic polyesters are highly viscous at high temperatures, hampering polycondensation. The TgS recorded for polyesters obtained by melt polymerization of isosorbide or isomannide with terephthaloyl chloride were 147 and 156 °C, respectively. 

For this reason, only di- and triallyl monomers have achieved commercial significance, and then only the esters. Since the cross-linked polymer occurring in this polymerization involves the side chains containing ester groups, they are also sometimes referred to industrially as polyesters. The di- and triallyl ester monomers are produced by the reaction of allyl alcohol with acids, acid anhydrides, or acid chlorides. Examples of monomers are diallyl phthalate (1) from phthallic anhydride, and triallyl cyanurate (II) from trichloro-5-triazine ... 

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... 

A recent publication described preparation of dendrimers from functional aliphatic polyesters that are based on 2,2-bis(hydroxymethyl)propionic acid [249]. A, Al -dicyclohexylcarbodiimide was used as the coupling agent in a double-stage convergent approach that reduced the number of synthetic and Uquid chromatographic steps required in the preparations and purifications. The hydroxyl functional dendrimers were then subjected to a variety of surface modifications by reactions with different acid chlorides [249]. 

A series of studies based on the combination of the difuran-dicarboxylic derivatives 11 and a wide choice of diols 12 were undertaken recently using all the classical procedures for the synthesis of polyesters 13, namely transesterification, condensation between the acid chloride moiety and the OH function and direct condensation. This comprehensive investigation included the structural characterization of all the polymers obtained, the determination of their molecular weight and molecular weight distribution, as well as of the thermal transitions and stability. From this broad set of results, interesting structure properties relationships could be drawn [4e]. 

Wholly aromatic polyesters from dihydric phenols and dicarboxyUc acid chlorides. They are characterized by high melting point (up to 500 °C), good thermal stability, and solubility in chlorinated solvents. Commercial polymers are produced by polycondensation of iso- and terephthalic acids with bisphenol A, having glass transition temperatures near 170 °C and the continuous use temperature of 140-150 °C. 

The properties similar to polycarbonates show polyarylate resins, synthesized usually by polycondensation process from terephthalic acid, isophthalic acid chloride, and BPA (Fig. 7.18). Polyarylates exhibit good impact strength, high deflection temperature, good chemical, thermal, weather and UV resistance as well as the dimensional stability higher than that of polycarbonates. Other important polymers with industrial significance, derived from BPA, are unsaturated polyesters (e.g., epoxyfuma-rate resins) [78], polyetherimides and polyether ether ketones (Fig. 7.18). 

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