Polylactic acids/polylactides

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

Since 1989, Cargill, has invested some 750 million to develop and commercialize polylactic acid (tradename NatureWorks). Its Nebraska plant, with an annual capacity of 140,000 metric tons, opened in 2002. Thus, polylactides, combining favorable economics with green sustainability, are poised to compete in large-volume markets that are now the domain of thermoplastic polymers derived from petrochemical sources. 

The use of biodegradable polymers, especially polylactic acid (PLA), in oral solid dosage forms has been reported in the literature. PLA has been used as a matrix for phenobarbital tablets (9). Similarly, the use of polylactide as a matrix for oral dosage form of naproxen has also been reported (10). 

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. 

Polymeric micropsheres, particularly those prepared from the biodegradable polylactide/ polyglycolide polymers, have been widely investigated as a means to achieve sustained parenteral drug delivery. The advantage of formulating the polymeric matrix as microspheres is the ability to administer them via a conventional needle and syringe as a suspension formulation, rather than as an implant (see below). Lupron depot formulations are available which can provide therapeutic blood levels of leuprolide acetate for up to four months. These products are presented as lyophilized polylactic acid microspheres which are reconstituted to form a suspension prior to administration. 

It is an aliphatic polyester derived from renewable resources, such as com starch, tapioca roots, chips or starch, or sugarcane. Polylactic acid or polylactide (PLA) can withstand temperatures up to 110 °C [69]. PLA is soluble in chlorinated solvents, hot benzene, tetrahydrofuran, and dioxane [70]. It can be processed like other thermoplastics into fiber (for example, using conventional melt spinning processes) and film. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist ... 

PLA to certain extend without the introduction of additives or other polymers. Although two general terms of polylactic acid and polylactide used to refer to PLA, the irony is, polylactides are prepared via ROP process while polylactic acid refers to PLA produced through polycondensation of lactic acid. 

Polylactide or Polylactic Acid (PLA) is a synthetic, aliphatic polyester from lactic acid (Figures 12.20 and 12.21). 

Figure 12.20 Ring opening polymerization of lactic acid dimer yielding polylactide (reproduced from Wikipedia Polylactic Acid).

PolylacHde, PolyglycoUde, and Copolymers. (Also known as polylactic acid and polyglycolic acid.) Degradation bioerosion polylactide R=CH3 polyglycolide R=H. 

Cell-culture studies have indicated that such structures promote cellular infiltration into the fibrillar network and can become densely populated in a reasonably short time. A number of natural and synthetic polymers have been successfully electrospun into fibrous scaffolds for the purpose collagen, elastin, gelatin, fibrinogen, polyglycolic acid, polylactic acid, polycaprolactone, polylactide-co-glycolide and polylactide-co-caprolac-tone. Recently published work indicates that an electrospun web formed... 

Polylactides from Lactones/Lactic Acid Polylactic Acid (PLA)... 

FIGURE P.l Number of works published since 1960 based on Scholars Portal Search (accessed on 28 Dec 09) using keywords polylactide , poly(lactic acid) , and polylactic acid . 

Polylactic acid, or polylactide, more commonly known as PLA, is a biodegradable polymer derived from 100% renewable resources. PLA, conq>arable to petroleum based plastic, is now used in a variety of industries including packaging, clothing, medicine and more. Classified as GRAS (generally recognized as safe) by FDA, PLA is a nonvolatile and odorless polymer [56 - 59]. 

Polylactic acid or polylactide (PLA) is a thermoplastic aliphatic polyester that can be derived from renewable resources, such as corn starch or sugarcanes. Although PLA has been known for more than a century, it has become of great commercial interest in recent years because of its renewability and degradability to natural metabolites. In addition, the properties of PLA can be varied over a wide range which makes it suitable to be used as a substitute to many petroleum based commodity plastics, such as polyolefins,... 

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