DLlactide

DL-lactide, or racemic lactide, is the racemic mixture of the two enantiomeric forms of lactide, the cyclic diester that arises from lactic acid. In this form, one lactic acid unit is D-lactide and the other is L-lactide, present in equal amounts. Lactide itself is formed by cyclization of two lactic acid molecules, and the DL form is the commercially common monomer used for polymerizing lactide into poly(lactic acid) (PLA) by ring-opening polymerization.

The stereochemistry of lactide influences the properties of the resulting PLA. Polymerization of DL-lactide yields an atactic, typically amorphous PLA with lower crystallinity and a different thermal behavior than PLA made from the homochiral LL- or DD-lactide, which can crystallize to form more rigid, semi-crystalline materials. As a result, DL-lactide is favored when processability and impact strength are prioritized, while enantiomerically enriched lactides are used to tailor crystallinity and mechanical properties.

Production and use: DL-lactide is produced by dehydration and cyclization of lactic acid, often under conditions that give the racemate directly. It is the form most commonly used as a commercial monomer for PLA production. PLA derived from DL-lactide is widely employed in biodegradable plastics, packaging, and various biomedical applications, where biodegradability and biocompatibility are advantageous.

Related stereoisomers include LL-lactide (L-lactide) and DD-lactide (D-lactide), which are enantiomeric to each other, and the meso LD-lactide, which is optically inactive.

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