Poly ester bond linkage

E Polynucleotide synthetases Responsible for the linkage of two poly- or oligo-nudeotide moieties to form polynucleotide chains 6.5.1. Ligases forming phosphoric ester bonds... 

Poly(ester anhydrides) and poly(ether anhydrides) presenting ether and/or ester linkages along the chain (in addition to anhydride bonds). Aliphatic and aromatic moieties are also present in the backbone. 

In order to exploit the inductive effect of the amide bond on the hydrolysis of the ester linkage in the polymer backbone the amide and ester linkage should be ideally separated by one methylene unit. It was apparent that a hydroxyacetamide structure would yield such an linkage. Hydroxyacetamide amidediols were obtained in high yields as the thermodynamically favorable product upon heating glycolic acid with alkane diamine neat with removal of w ater (Barrows, 1982, 1988, 1994). The polymer is then obtained either by trans esterification polymerization of the diol (bis-hydroxyacetamides) with the desired diester of the diacid or by the reaction of bis-hydroxyacetamides with diacid chlorides (Scheme 3) (Barrows 1982, 1988, 1994). Poly (ester-amides) can be prepared from a wide variety of different bis-hydrox acetamide amidediols and diacids. 

A fraction of the ester linkages can be substituted with amide linkages, which modifies interchain hydrogen bonding. Examples are the BAK poly(ester amides) previously manufactured by Bayer. 

Urethane bonds are also amide mimetics, so they can be hydrolyzed by enzymes such as human neutrophil elastase and pancreatic elastase [62], PUs containing ester linkages degrade faster compared to those with ether linkages. The degradation of poly(ester urethane urea) by porcine pancreatic elastase was 10 times faster than that of poly(ether urethane urea). 

Poly(a-ester)s, the most expansively studied class of biodegradable polymer, contain aliphatic ester linkages in their backbone which can be cleaved hydrolytically. It is reported that mere aliphatic polyesters with practically small aliphatic chains between ester bonds can decompose over the time needed for the majority of the biomedical applications. Poly(a-ester)s demonstrate enormous diversity and synthetic flexibility and, depending on the monomeric units, can be synthesized from a variety of monomers via condensation polymerization and ring-opening routes [19]. Poly(glycolic acid) and the stereoisomers of poly(lactic acid) are the most expansively investigated poly(a-ester)s polymers. 

The ester bond is the typical linkage to use in the design of alkali-labile surfactants. The concept is by no means new. Poly(ethylene glycol) (PEG) esters of fatty acids have been around for a long time. They are produced by ethoxylation of the fatty acid the product obtained is a mixture of roughly... 

Yen, F. S., Lin, L. L., Hong, J. L. (1999), Hydrogen-bond interactions between urethane-urethane and urethane-ester linkages in a liquid crystalline poly(ester-urethane). Macromolecules, 32, 3068-79. 

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