Lactide Synthesis and Chirality Control for Polylactic acid Production

Abstract

Polylactic acid (PLA) is a very promising biodegradable, renewable, and biocompatible polymer. Aside from its production, its application field is also increasing, with use not only in commodity applications but also as durables and in biomedicine. In the current PLA production scheme, the most expensive part is not the polymerization itself but obtaining the building blocks lactic acid (LA) and lactide, the actual cyclic monomer for polymerization. Although the synthesis of LA and the polymerization have been studied systematically, reports of lactide synthesis are scarce. Most lactide synthesis methods are described in patent literature, and current energy-intensive, aselective industrial processes are based on archaic scientific literature. This Review, therefore, highlights new methods with a technical comparison and description of the different approaches. Water-removal methodologies are compared, as this is a crucial factor in PLA production. Apart from the synthesis of lactide, this Review also emphasizes the use of chemically produced racemic lactic acid (esters) as a starting point in the PLA production scheme. Stereochemically tailored PLA can be produced according to such a strategy, giving access to various polymer properties.

Adsorption and Reactive Desorption on Metal–Organic Frameworks: A Direct Strategy for Lactic Acid Recovery

“…On the product side, catalytic routes allow the efficient conversion of LA into biodegradable plastics [e.g., poly(lactic acid) (PLA)], green solvents (e.g., lactate esters), or bio‐based chemicals (e.g., acrylic acid) . Mainly driven by the global production capacity of PLA, which is projected to grow annually with 18.8 % and reach over 1.2 million tons in 2020, the demand for LA is expected to follow a similar trend …”

Bio‐Acrylates Production: Recent Catalytic Advances and Perspectives of the Use of Lactic Acid and Their Derivates

“…LA can be converted, among others, to acetaldehyde, 1,2‐propanediol, 2,3‐pentanedione or it may undergo dimerization to lactide . However, the conversion of LA to AA is the most widely studied route.…”

“…LA can be converted, among others, to acetaldehyde, [71][72][73] 1,2propanediol, [74][75][76] 2,3-pentanedione [77][78][79][80][81] or it may undergo dimerization to lactide. [82][83][84][85] However, the conversion of LA to AA is the most widely studied route. Although several reviews describe the LA-to-AA chemical route [2,4,86,87] together with a discussion about the reaction mechanisms, [88] we are aiming for a more structured updated summary of the existing literature on this LA-to-AA reaction and we will present a clear separation of lactic acid based studies from those based on derivatives of lactic acid.…”

Biotic and Abiotic Synthesis of Renewable Aliphatic Polyesters from Short Building Blocks Obtained from Biotechnology

“…Nevertheless,p roteases such as papain, bromelain, trypsin, and a-chymotrypsin showedamuch higherr eactivity towards the synthesis of polyamides. However,b ecause e-ROP of lactones and lactides have been largely investigated and reviewed, [89,[225][226][227][228][229][230] they are not discussed herein. Enzymatic step-growth polymerization of polyesters Similar to chemical polymerization, three polymerization modesc an be envisagedf or lipase-catalyzed polyesters ynthesis:1 )step-growth polycondensation, 2) enzymatic ring-opening polymerization (e-ROP), and 3) ac ombination of ROP and polycondensation.…”