Polylactic acid lactide

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

Similar to pure polyglycoHc acid and pure polylactic acid, the 90 10 glycolide lactide copolymer is also weakened by gamma irradiation. The normal in vivo absorption time of about 70 days for fibrous material can be decreased to less than about 28 days by simple exposure to gamma radiation in excess of 50 kGy (5 Mrads) (35). 

Braided Synthetic Absorbable Sutures. Suture manufacturers have searched for many years to find a synthetic alternative to surgical gut. The first successful attempt to make a synthetic absorbable suture was the invention of polylactic acid [26023-30-3] suture (15). The polymer was made by the ring-opening polymerization of L-lactide [95-96-5] (1), the cycUc dimer of L-lactic acid. 

Polylactic acid (PLA) has been produced for many years as a high-value material for use in medical applications such as dissolvable stitches and controlled release devices, because of the high production costs. The very low toxicity and biodegradability within the body made PLA the polymer of choice for such applications. In theory PLA should be relatively simple to produce by simple condensation polymerization of lactic acid. Unfortunately, in practice, a competing depolymerization process takes place to produce the cyclic lactide (Scheme 6.10). As the degree of polymerization increases the rate slows down until the rates of depolymerization and polymerization are the same. This equilibrium is achieved before commercially useful molecular weights of PLA have been formed. 

Lactic acid is hygroscopic and will form condensation products such as polylactic acids on contact with water. The equilibrium between the polylactic acids and lactic acid is dependent on concentration and temperature. At elevated temperatures lactic acid will form lactide, which is readily hydrolyzed back to lactic acid. 

Abbreviations A, acetone ASES, aerosol solvent extraction system DM, dichloromethane DMF, A/,A/-dimethyl-formamide E, ethanol GAS, gas antisolvent process H, hexane HYAFF-11, hyaluronic acid benzylic ester I, isopropanol PAN, polyacrylonitrile PCA, precipitation with compressed antisolvent PCL, polycaprolactone PHB, poly(p-hydroxybutyric acid) PLA, polylactic acid PLGA, poly(lactic-co-glycolic acid) SAS, supercritical antisolvent process SEDS, solution enhanced dispersion by supercritical fluids TFE, 2,2,2-trifluoroethanol Triblock polymer, p poly(L-lactide-CO-D,L-lactide-co-glycolide)(62.5 1 2.5 25). 

Chang, Y.-N., Mueller, R., lannotti, E. Use of low MW polylactic acid and lactide to stimulate growth and yield of soybeans. Plant Growth Reaul. 1996,19, 223-232. 

Polylactic acid (PEA) is probably the best-known biobased polymer. It is made from glucose by fermentation to its monomer lactic acid. Two molecules of lactic acid are then condensed into the dimer lactide, which is subsequently ring-opened and polymerized to PLA in the presence of a catalyst. 

Polylactic acid (PLA) has been known for many years but use of this biodegradable plastic polymer was largely confined to internal surgical stitching due to the relatively high cost. Recent advances in the process for fermentation of com starch to produce lactate, coupled with chemical lactide formation, have resulted in a cost that is economically attractive. Cargill Dow Polymers have announced investments of over 300 million in a new facility in... 

Lactic acid reacts with diacid or diol to form telechelic polylactic acid, then through further a linking reaction it forms high-molecular-weight lactic acid copolymers [33, 44, 45]. Polymerization of a racemic mixture of L- and D-lactides usually leads to the synthesis of poly-DL-lactide (PDLLA)which is amorphous. Use of stereospecific catalysts can result in heterotactic PLA which is found to show crystallinity [46, 47]. The degree of crystallinity and many associated properties are greatly controlled by the ratio of D to l enantiomers in the polymer [48]. 

Polylactic Acid Polylactic acid (PLA) is a thermoplastic, ahphatic polyester that can be synthesized from biologically produced lactic acid. Currently, the major production of polylactic acid is from the ring-opening polymerization of the lactide [43, 44]. This material has been used extensively in the medical field for sutures, staples, and the like and as such is very expensive. Recently, April 2002, Cargill-Dow has opened a large-scale production facility whereby PLA is being produced at a low cost for nonmedical applications ... 

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