Lactic 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 ... 

Figure 13.1.4 The synthesis of poly(lactic acid) (PLA) by a ring-opening polymerization of the cyclic diester of lactic acid (lactide).

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). 

A process of ring-opening polymerization in which a cyclic dimer of lactic acid (lactide) is melted and pol5m erized (6,7)... 

CHEMISTRY AND PRODUCTION OF LACTIC ACID, LACTIDE, AND POLY(LACTIC ACID)... 

M. Mutsuga, U. Kawamura, K. Tanamoto, Migration of lactic acid, lactide and ohgomers from polylactide food-contact materials. Food Addit. Contam. 2008, 25, 1283-1290. 

Migrants from PLA may include lactic acid, the linear dimer of lactic acid (lactoyl lactic acid), other oligomers of PLA ( = 3-13), and the cyclic dimer of lactic acid (lactide). Their chemical structures are shown in Figure 13.1. 

Polylactic acid (PLA) is the world s most popular synthetic biodegradable polymer and has a widespread use in the biomedical field. It maybe obtained directly from lactic acid by condensation polymerization or, more commonly, by ring-opening polymerization from the cyclic dimer of lactic acid lactide. Lactide is a chiral molecule that exists in three isomeric forms D(-), L(+) and racemic (D,L) lactide. Consequently, the polymerization of this monomer can lead to the formation of three different forms of polylactide poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), and poly-D,L-lactic acid (PDLLA). The general representation of the chemical structure of PLA is presented in Figure 16.10. 

Figure 11.4 Synthesis of lactic acid, lactide and polyjlaclic acid).

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