Carboxylic acids polyesters

This section presents and discusses a few examples of reactive blending during the preparation of polyester and polyamide blends, by reaction of epoxy/carboxylic acid (polyesters blends) and anhydride/amine (polyamide blends) groups. 

The carboxylic acid produced m the greatest amounts is 1 4 benzenedicarboxylic acid (terephthahc acid) About 5 X 10 Ib/year is produced m the United States as a starting material for the preparation of polyester fibers One important process converts p xylene to terephthahc acid by oxidation with nitric acid... 

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

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. 

Carboxylic acid hydiazides are prepared from aqueous hydrazine and tfie carboxylic acid, ester, amide, anhydride, or halide. The reaction usually goes poody with the free acid. Esters are generally satisfactory. Acyl halides are particularly reactive, even at room temperature, and form the diacyl derivatives (22), which easily undergo thermal dehydration to 1,3,4-oxadiazoles (23). Diesters give dihydtazides (24) and polyesters such as polyacrylates yield a polyhydrazide (25). The chemistry of carboxyhc hydrazides has been reviewed (83,84). 

In order to become useful dmg delivery devices, biodegradable polymers must be formable into desired shapes of appropriate size, have adequate dimensional stability and appropriate strength-loss characteristics, be completely biodegradable, and be sterilizahle (70). The polymers most often studied for biodegradable dmg delivery applications are carboxylic acid derivatives such as polyamides poly(a-hydroxy acids) such as poly(lactic acid) [26100-51-6] and poly(glycolic acid) [26124-68-5], cross-linked polyesters poly(orthoesters) poly anhydrides and poly(alkyl 2-cyanoacrylates). The relative stabiUty of hydrolytically labile linkages ia these polymers (70) is as follows ... 

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

Polyamides and Polyesters Step-Growth Polymers 818 21.10 Spectroscopy of Carboxylic Acid Derivatives 822... 

Polyesters. The polycondensation prods of di-carboxylic acids with dihydroxy alcohols. 

In die presence of oxygen, more complex thermo-oxidative processes occur in polyesters containing aliphatic moieties. They result in crosslinked products and in the formation of compounds such as aldehydes, carboxylic acids and vinyl esters, as reported in the case of PET.93,94 On the other hand, the presence of oxygen has little effect on the thermal resistance of wholly aromatic polyesters below 550°C. Above this temperature a char combustion process takes place.85... 

Phenolic compounds are weaker nucleophiles and better leaving groups than aliphatic alcohols. They do not yield polyesters when reacted with carboxylic acids or alkyl carboxy lates. The synthesis of polyesters from diphenols is, therefore, generally carried out through the high-temperature carboxylic acid-aryl acetate or phenyl ester-phenol interchange reactions with efficient removal of reaction by-product (Schemes 2.10 and 2.11, respectively). 

Since anhydrides are much more reactive than carboxylic acids, reaction kinetics is controlled by the second step. The scope and apphcations of this reaction are the same as direct polyesterification but are practically limited to the synthesis of unsaturated polyesters and alkyd resins from phtliahc and maleic anhydrides (see Sections 2.4.2.1 and 2.4.23). 

Similarly, triphenylphosphine dichloride (TPPCI2) can activate aromatic carboxylic acids in pyridine through the formation of acyloxyphosphonium salts (Scheme 2.30).313 A side reaction between tire intermediate acyloxyphosphonium species and a second carboxyl endgroup leading to the formation of anhydrides has been reported.313 This chain-limiting reaction decreases tire molar mass, while the presence of anhydride linkages in tire chains adversely affects the thermal and hydrolytic stability of the final polyester. 

Adipic acid, 219.2 g (1.5 mol), and 77.6 g (1.25 mol) of 1,2-ethanediol are weighed into a 500-mL glass reactor equipped with a mechanical stirrer, a nitrogen inlet, and a distillation head connected to a condenser and a receiver fiask. The reactor is placed in a salt bath preheated at 180°C and the temperature is dien raised gradually to 220°C (see note at end of procedure) until the greater part of water has been removed (3 h). The reactor is cooled down to 160°C and vacuum is applied slowly to ca. 0.07 mbar (30 min). Temperature is ramped to 220°C (see note below) at a rate of l°C/min and reaction is continued for an additional 90 min. At the end of reaction, the carboxylic acid endgroup content is close to 1.90 mol/kg. No purification of final polyester is carried out. 

Fourier transform infrared (FTIR) spectroscopy (NaCl) shows no remaining carboxylic acid (1696 cm-1, carbonyl) but only ester groups (1736 cm 1, carbonyl) Mn(SEC) = 6530 Mn(1H NMR) = 1640 theory for third generation Mn = 2570.65 Polyesters of higher generation were synthesized according to this pseudo-one-step procedure and were analyzed by SEC, VPO, and 111 NMR.65... 

Isocyanates react with carboxylic acids to form amides, ureas, anhydrides, and carbon dioxide, depending on reaction conditions and the structure of the starting materials (Scheme 4.13). Aliphatic isocyanates more readily give amides. Aromatic isocyanates tend to react with carboxylic acids to first generate anhydrides and ureas, which at elevated temperatures (ca. 160°C) may further react to give amides. In practice, the isocyanate reaction with carboxylic acid is rarely utilized deliberately but can be an unwanted side reaction resulting from residual C02H functionality in polyester polyols. 

In condensation polymers, the monomers are linked together by condensation reactions, like those used to form ester or amide links. Polymers formed by linking together monomers that have carboxylic acid groups with those that have alcohol groups are called polyesters. Polymers of this type are widely used to make artificial fibers. A typical polyester is Dacron, or Terylene, a polymer produced from the... 

Most condensation polymers are formed by the reaction of a carboxylic acid with an alcohol to form a polyester or with an amine to form a polyamide. 

As a first step in the prepartion of polymers patterned after the repeating unit of nonactin 56, Moore and Kelley53 synthesized 3,8-dioxabicyclo[3.2.1 ]octan-2-one 57 and its corresponding polyester 58. The monomer was prepared from 5-hydroxy-methylpyran-2-carboxylic acid in overall yield of 20%. It was heated with a catalytic amount of tert-butoxytitanate under nitrogen for 3 hr at 100 °C. The temperature... 

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

Ethoxylation of the carboxylic acid end groups of aliphatic polyesters significantly changes the biodegradation rate as well as the crystallinity of these materials (41). 

An implication of the kinetic analysis presented in Sec. IV.A is that the rate of chain scission of polyesters can be retarded by endcapping to reduce the initial carboxylic acid end-group concentration. Alternatively, the rate may be increased by acidic additives that supplement the effect of the carboxy end groups. The first expectation was confirmed by partial ethanolysis of high molecular weight... 

Poly(malic acid) is a biodegradable and bioadsorbable water-soluble polyester having a carboxylic acid in the side chain. The chemoenzymatic synthesis of poly(malic acid) was achieved by the lipase-catalyzed polymerization of benzyl (3-malolactonate, followed by the debenzylation. The molecular weight of poly(benzyl (3-malolactonate) increased on copolymerizafion with a small amount of (3-PL using lipase CR catalyst. ... 

A methacryl-type polyester macromonomer was synthesized by lipase PF-catalyzed polymerizahon of DDL using vinyl methacrylate as terminator ( terminator method ), in which the vinyl ester terminator was present from the beginning of the reachon (Scheme 17). In using divinyl sebacate as terminator, the telechelic polyester having a carboxylic acid group at both ends was obtained. Various non-protected thiol compounds were used as inihator or terminator for the thiol end-funchonalizahon of poly(8-CL). ... 

In the first part of this activity, you will prepare a polyester. As the name polyester implies, this polymer contains many ester functional groups. One technique for preparing an ester is by the reaction of a carboxylic acid with an alcohol. RCOOH + R OH —> RCOOR + H20... 

If the carboxylic acid has two carboxyl functional groups (a dicarboxylic acid) and if the alcohol has two hydroxyl functional groups (a diol), a polyester will result nHOOC—R—COOH + nHO—R —OH —> +OOC—R—COO—R +n + nH20. 

Here the polymer grows by successive esterification with elimination of water and no termination step. Polymers formed by linking monomers with carboxylic acid groups and those that have alcohol groups are known as polyesters. Polymers of this type are widely used for the manufacture of artificial fibers. For example, the esterification of terephthalic acid with ethylene glycol produces polyethylene terephthalate. 

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]. 

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