Hydrolysis of polyesters

Effect of chain structure on the hydrolysis of polyester polyurethanes... 

Schollenberger added 2% of a polycarbodiimide additive to the same poly(tetra-methylene adipate) urethane with the high level of acid (AN = 3.66). After 9 weeks of 70°C water immersion, the urethane was reported to retain 84% of its original strength. Carbodiimides react quickly with residual acid to form an acyl urea, removing the acid catalysis contributing to the hydrolysis. New carbodiimides have been developed to prevent hydrolysis of polyester thermoplastics. Carbodiimides are also reported to react with residual water, which may contribute to hydrolysis when the urethane is exposed to high temperatures in an extruder [90]. 

Cationic accelerants vary in their efficacy [161]. Other types of accelerant have also been evaluated. In one study [162], comparisons were made between tetra-ethylammonium bromide, benzyltriethylammonium chloride, polyfdiallyldimethylammonium chloride) and the diethyldimethylammonium derivative of a benzenesulphonate polyglycol ester. It was found that the cationic polymers had a greater effect than the simple quaternary ammonium compounds of lower molecular mass. This effect was attributed to the capability of the polymers to enter into hydrophobic interaction with the fibre surface. Ethylenediamine has also been found to accelerate the alkaline hydrolysis of polyester [163]. 

Hydrolysis of Polyesters Used in Electrical and Civil Engineering... 

Hydrolysis of Polyester by Lipase. Aliphatic polyester, PEA and PCL were hydrolyzed by lipases from Achromobacter sp., C. cylindracea,... 

Table I. Hydrolysis of Polyesters by R. delemar and R. arrhizus Lipases...

Hydrolases in Polymer Chemistry Part III Synthesis and Limited Surface Hydrolysis of Polyesters and Other Polymers... 

Herzog K, Muller RJ, Deckwer WD (2006) Mechanism and kinetics of the enzymatic hydrolysis of polyester nanoparticles by lipases. Polym Degrad Stab 91 2486-2498... 

Another contribution to drug release was indicated in a previous paper (5) which reported on the hydrolysis of polyesters catalyzed by encapsulated amine drug such as thioridazine. The microsphere batches prepared for this investigation have identical drug loadings. Therefore, any contribution due to the amine drug should be equal for all the samples being compared. 

Tokiwa, Y., Suzuki, T. Takeda, K. (1986). Hydrolysis of polyesters by Rhizopus arrhizus lipase. Agricultural and Biological Chemistry, 50, 1323-5. 

The mechanism of stabilization of polyesters by carbodiimides is based on their rapid reaction with carboxylic acids, generated in the hydrolysis of polyesters. Carboxylic acids are catalysts for further hydrolysis of the polyesters. 

Oligomeric carbodiimides are useful stabilizers for ester based polymers, such as polyesters, polyester based polyurethanes, polyether based polyurethanes, polyether based poly(urethane ureas) and polycarbonates. The scavenging of carboxyl end groups or carboxyl groups, generated in the hydrolysis of polyesters, with carbodiimide prevents hydrolysis of the polymers caused by the catalytic effect of the carboxyl groups. Neumann... 

Figure 14. Base hydrolysis of polyester showing cleavage...

Figure 15. Base hydrolysis of polyester (total Na fn, N O,. OlH) insoluble...

Polyester polyols have an intrinsic defect they are liable to hydrolyse under high humidity/temperature conditions. To prevent the hydrolysis of polyester-based polyurethanes a worldwide research effort, led to the synthesis of polyester polyols with improved hydrolysis resistance [1, 6-8, 12, 13]. 

Base-catalyzed hydrolysis of polyesters is hypothesized to be the predominant mechanism by which polyesters hydrolyze in physiologic conditions. The mechanism of base-catalyzed hydrolysis is shown in Scheme 1. The first step is the attack of the hydroxide anion to the carbonyl carbon of the ester. 

Tokiwa Y, Suzuki T (1977) Hydrolysis of polyesters by lipases. Nature 270 76—78 Tuominen J, Kylma J, Kapanen A et al (2002) Biodegradatirai of lactic acid based polymers under controlled composting conditions and evaluation of the ecotoxicological impact. Biomacromolecules 3 445 55... 

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