Lactide polylactide

Lactide can be found as L-lactide, D-lactide, the racemic mixture thereof (namely raolactide), and meso-lactide. Polylactides can thus exhibit different microstruc-... 

Polylactide is the generaUy accepted term for highly polymeric poly(lactic acid)s. Such polymers are usuaUy produced by polymerization of dilactide the polymerization of lactic acid as such does not produce high molecular weight polymers. The polymers produced from the enantiomeric lactides are highly crystalline, whereas those from the meso lactide are generaUy amorphous. UsuaUy dilactide from L-lactic acid is preferred as a polymerization feedstock because of the avaUabUity of L-lactic acid by fermentation and for the desirable properties of the polymers for various appUcations (1,25). 

Polylactic acid, also known as polylactide, is prepared from the cycHc diester of lactic acid (lactide) by ring-opening addition polymerization, as shown below ... 

Polymerization of D,L-lactide to polylactide was also achieved using monomeric tin(ll) amidinates (cf. Schemes 48 and and the mono... 

The use of polylactides for delivery of insect hormone analogs and other veterinary compounds (115,116) has been studied. Microspheres, pellets, and reservoir devices based on polyglycolide, poly-(DL-Iactide), poly(L-lactide), and various copolymers have been used to deliver methoprene and a number of juvenile hormone analogs. ... 

Jensen et al. reported the stereoselective polymerization of D,L-lactide with dibenzyloxidezinc(2,4,6-trimetylphe-nyimidazol-2-ylidene), which was synthesized as shown in Scheme 39.100 Surprisingly, a mixture of the heterocarbene and benzyl alcohol was a better catalyst for polylactide formation than the zinc complex, and unlike 50 the mixture produced heterotactically enriched polylactide. 

Chisholm et al. synthesized organozinc compounds with bulky biphenolates as catalysts for the ring-opening polymerization of lactides.196 The protonolysis of diethyzinc by the biphenols, in the presence of diisopropylmethanol, afforded the polycyclic, trimetallic zinc-di(ethylzinc) pre-catalyst 135, which polymerizes /m -lactide to polylactide, enriched in isi- and. sir-tetrads (Scheme 85). 

Poly(lactide-co-glycolide) (PLGA), 13 741 Polylactide nanocomposites, improved, 20 308... 

Tasaka F, Ohya Y, Ouchi T (2001) One-pot synthesis of novel branched polylactide through the copolymerization of lactide with mevalolactone. Macromol Rapid Commun 22 820-824... 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization of Lactides and Glycolides Preparation of Polylactides, Polyglycolide, and Poly(lactide-co-glycolide). 219... 

Polyesters, specifically polylactides and poly(lactide-co-glycolide)s have played a critical role in the development of polymer-based CR technologies. The biocompatibility and the well-established safety profiles of PLA and PLGA polymers have made them the polymer of choice for CR applications. However the off-patent status of these polymers makes them freely available for research in industry as well as academia. This has led to a vast number of patents covering various applications of these polymers within the drug delivery sector. Due to these issues, very limited scope remains to utilize these polymers to reformulate generic, off-patent drugs. 

Figure 4 A typical reaction scheme for the synthesis of polylactides. By varying the ratio of the initiator (in this case propylene glycol) to lactide, the molecular weight of the final polymer could be controlled as desired.

The conformations of stereoregular poiyIL-lactide and regularly alternating polyiL.D-lactide) confined to occupy cylinders of varying radii are determined in an effort to learn if either polylactide could be incorporated in the narrow channels of its inclusion compound with urea. 

Hietala EM, Maasilta R Valimaa T et al. Platelet responses and coagulation activation on polylactide and heparin-polycaprolactone-L-lactide-coated polylactide stent struts. J Biomed Mater Res A2003 67(3) 785—791. 

Much has been written about Cargill Dow LLC s polylactide (PLA) polymer, also known as NatureWorks PLA. PLA is a thermoplastic produced from biomass sugars by fermentation. The fermentation product, lactic acid, is converted into a lactide that is purified and polymerized using a special ring-opening process (18). 

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)... 

Keywords Carbon dioxide and epoxides copolymerization Group 13 metal catalysts Group 3 metal catalysts Lactide polymerization Polycarbonate Polylactide... 

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 most effective, and commercially applied, method to produce polylactide is via the ring-opening polymerization of lactide. This process is initiated by metal complexes and proposed to occur via a coordination-insertion mechanism, as illustrated in Fig. 2. The most common initiators for this polymerization are Lewis acidic metal alkoxide or amide complexes. Key initiator criteria are sufficient Lewis acidity to enable binding and activation of the lactide unit and a labile metal alkoxide (or amide) bond so as to enable efficient insertion. 

Due to the chiral nature of lactic acid, several distinct forms of polylactide exist poly-L-lactide (PLLA) is the product resulting from polymerization of L,L-lactide (also known as L-lactide). PLLA has a crystallinity around 37%, a glass transition... 

NatureWorks LLC has set up a 300 million plant at Blair, NE, which is capable of producing about 140,000-tons/year of poly-lactide polymers from com sugar. It employs a fermentation process to produce two chiral isomers of lactic acid from glucose, which are then cracked to form three lactide isomers. The isomers are subsequently polymerized to polylactide. 

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