Polylactide, degradation

McNeill, I.C. and Leiper, H.A. (1985) Degradation studies of some polyesters and polycarbonates 2. Polylactide Degradation under isothermal conditions, thermal degradation mechanism and photolysis of the polymer. Polymer Degradation and Stability, 11,309-326. 

Key words poly(alpha-hydroxy acids), degradation rate, polyglycolide, polylactide, degradation. 

Pranamuda H., Tokiwa Y, Tanaka H. Polylactide degradation by an Amycolatopsis sp., Appl Environ. Microbiol 63 (1997) 1637. 

Figure 8.3 Postulated reactions of polylactide degradation, (a) Intramolecular transesterfication (back-biting) (b) Intramolecular transesterfication (c) Intermolecular transesterfication (d) Hydrolysis (e) Pyrolytic elimination...

Meinander K, Niemi M, Hakola J S, Selin J F (1997), Polylactides-Degradable pol3miers for fibers and films , Macromol Symp, 123, 147-153. 

Polycaprolactones (see also Section 25.11), although available since 1969, have only recently been marketed for biodegradable purposes. Applications include degradable film, tree planting containers and slow-release matrices for pharmaceuticals, pesticides, herbieides and fertilisers. Its rate of biodegradability is said to be less than that of the polylactides. 

Other interesting polyesters of practical relevance are polylactides that are considered to be biologically degradable. Polylactides are prepared by a ring opening... 

DL-Polylactic acid, for the most part, was found to erode in about 12 months. Slow degradation of DL-polylactic acid often becomes a limitation on its use. This rate can be accelerated appreciably by copolymerizing with up to 50 mol% glycolide to yield complete erosion in as fast as 2 to 3 weeks. Incorporation of glycolide into the polylactide chain alters crystallinity, solubility, biodegradation rate, and water uptake of the polymer. 

Keywords. Controlled drug delivery, Drug release, Microspheres, Degradation, Erosion, Polylactide, Poly(glycolide-co-lactide), Poly(e-caprolactone), Poly(hydroxyalkanoates) Polyanhydrides, Polycarbonates, Poly(orthoesters), Poly( l,5-dioxepan-2-one)... 

Following the recognition of polylactide as a promising biomedical polymer, attention was drawn to related polyesters in the search for new degradable polymers in similar applications. PCL was recognized as a biodegradable and nontoxic material. 

Abstract. This paper reviews the degradation behavior of aliphatic polyesters of current interest, including polylactide, polycaprolactone, poly(3-hydroxybutyrate) and their copolymers. Special focus is given to degradation products formed in different abiotic and biotic environments. The influence of processing and processing additives on the properties and degradation behavior is also briefly discussed. 

Keywords. Polylactide, Polycaprolactone, Poly(3-hydroxybutyrate), Degradation, Degradation products... 

Gas chromatography-mass spectrometry (GC-MS), liquid chromatography (LC), enzymatic assays, and capillary zone electrophoresis (CZE) have been used to monitor abiotic and biotic degradation products of polylactide and its copolymers [35,37,115,126-128]. In abiotic aqueous environments the degra-... 

Polylactide is a degradable polyester, formed by the ring-opening polymerization of lactide or the condensation polymerization of lactic acid. Lactide is produced from lactic acid, which derives from the fermentation of D-glucose, which is usually harvested from high-starch-content crops, such as com or sugar beet (Fig. 1). 

The present paper reports on a study which was conducted to investigate the effect of NaOH on the in vitro release profiles of microspheres prepared with polylactides (2) Since these polyesters degrade by hydrolysis (4), it is possible that the molecular weight of the polymers can be decreased by the alkaline pH of the sodium oleate emulsifier solution (pH 10) during fabrication. This in turn could affect the release kinetics of the microspheres. 

These polylactides are known to degrade by hydrolysis (4.) Therefore, the most obvious explanation is that the molecular weight of the polymer is decreased by the NaOH. It has been reported (6) that drug release is increased when the polymer molecular weight is lowered. This would then account for the enhanced drug release observed. 

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