Polymer esters carboxylic acids

Preparation of Esters by Use of a Polymer-Supported Carboxylic Acid Imidazolide... 

The terminal carhanionic sites of "living" polymers can be reacted with various electrophilic compounds of yield (o)-functional polymers. Esters, nitriles, acid chlorides, anhydrides, lactones, epoxides, benzyl or allyl halogenides have been used for their high reactivity with metal organic sites, to yield appropriate functions.2 Carbon dioxide is also an efficient reagent to yield terminal carboxylic functions. 

Polymer-bound active esters 26 were prepared from a 1-hydroxyben-zotriazole (HOBt) functionalized polymer and carboxylic acids in the presence of tripyrrolidinyl-bromophosphonium hexafluorophosphate (Py-... 

Telechelic dienes for metathesis polycondensation, containing functional groups such as those in alcohols, esters, carboxylic acids and imides, can be obtained via acyclic diene metathesis depolymerisation [64,65]. They can then be used in further reactions to create hydrophobic polyurethanes and other special-purpose polymers [1]. 

The deprotonation-substItution approach has also been used to prepare polymers with carboxylic acid and ester and carboxylated salt moieties attached to the phosphazene. (25) THF solutions of the parent polymer were treated with sufficient n-BuLi to facilitate deprotonation of 10, 25, or 50% of the methyl substituents. The resulting polymer anions were then treated with anhydrous carbon dioxide to produce the carboxylate salts 11 (eq 10). These salts were Isolated by removal of the solvent or were used in further reactions with dilute aqueous acid solutions (eq 11) or with p-nitrobenzylbromide (eq 12) to give the carboxylic acids, 12, or esters, 13, respectively. 

ADMET polymers containing carboxylic acid groups were synthesized by polymerizing the corresponding a,m-diene with a pendant 1-ethoxyethyl ester, which was converted to the carboxylic acid after polymerization (Figure 13.13) [101]. 

Actually these polyesters might also have had carboxylic acid end-groups, which would react even more readily with epoxy to form ester-linked graft copolymers. In several studies, the epoxy group was clearly reacted with polymers containing carboxylic acid groups, producing compatibility in this way [141, 144, 145, 150, 152, 153]. 

While there is no simple rule about the structures found in a polymer, the most common polymers have only a few organic functional groups, that repeat over and over to make the macromolecules. Of the groups shown in Figure 1.3, alkanes, esters, urethanes, carbonates, aryls, silanes, amides, and imides are commonly found in the backbone of polymers. Alcohols, carboxylic acids, and amines are either reactive parts of monomers or can be found in polymer side groups. 

Ester interchange reactions are valuable, since, say, methyl esters of di-carboxylic acids are often more soluble and easier to purify than the diacid itself. The methanol by-product is easily removed by evaporation. Poly (ethylene terephthalate) is an example of a polymer prepared by double application of reaction 4 in Table 5.3. The first stage of the reaction is conducted at temperatures below 200°C and involves the interchange of dimethyl terephthalate with ethylene glycol... 

Pyrazine, tetrahydro-, 3, 177, 178 Pyrazine, 1,2,3,4-tetrahydro-synthesis, 3, 177 Pyrazine, 2,3,5-tri-t-butyl-synthesis, 3, 185 Pyrazine, 2,3,5-trichloro-nucleophilic substitution, 3, 176 Pyrazine, 2-vinyl-polymers, 1, 290-291 Pyrazine-3-carboxylic acid, 2-amino-methyl ester... 

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... 

Although, the enzymatic reaction of esters with amines or ammonia have been well documented, the corresponding aminolysis with carboxylic acids are rarer, because of the tendency of the reactants to form unreactive salts. For this reason some different strategies have been used to avoid this problem. Normally, this reaction has been used for the preparation of amides of industrial interest, for instance, one of the most important amides used in the polymer industry like oleamide has been produced by enzymatic amidation of oleic acid with ammonia and CALB in different organic solvents [10]. 

The choice of the alcohol permits manipulation of the structure of the polymer. Water and monohydric alcohols afford linear chains with carboxylic acid and ester end groups, respectively. Polyhydroxy initiators afford a route to ester end-blocked star and comb polymers (Fig. 4) (47). 

This equation assumes that the carboxylic acid group is not ionized in the polymer bulk and functions by hydrogen-bonding to the ester groups. For a small number of chain scissions, both the ester and water concentrations may be considered constants, and Eq. 4 simplifies to Eq. 5. 

However, in subsequent work it was found that carboxylic acid groups readily add to ketene acetals to form carboxyortho ester linkages (24). These are very labile linkages and on hydrolysis regenerate the carboxylic acid group which then exerts its catalytic function. Because carboxylic acids add so readily to ketene acetals, very labile polymers can be prepared by the addition of diacids to diketene acetals. The utilization of such polymers is currently under investigation. 

Finally, a new water-soluble polyphosphazene was recently synthesized that has the structure shown in 36 (46). This polymer has two attributes as a biomedical macromolecule. First, the pendent carboxylic acid groups are potential sites for condensation reactions with amines, alcohols, phenols, or other carboxylic acid units to generate amide, ester, or anhydride links to polypeptides or bioactive small molecules. Second, polymer forms ionic crosslinks when brought into contact with di- or trivalent cations such as Ca or Ai3+. The crosslinking process converts the water-soluble polymer to a hydrogel, a process that can be reversed when the system... 

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