Polylactide polymerization

Polylactide is the generaUy accepted term for highly polymeric poly(lactic acid)s. Such polymers are usuaUy produced by polymerization of dilactide the polymerization of lactic acid as such does not produce high molecular weight polymers. The polymers produced from the enantiomeric lactides are highly crystalline, whereas those from the meso lactide are generaUy amorphous. UsuaUy dilactide from L-lactic acid is preferred as a polymerization feedstock because of the avaUabUity of L-lactic acid by fermentation and for the desirable properties of the polymers for various appUcations (1,25). 

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

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

Polymerization of D,L-lactide to polylactide was also achieved using monomeric tin(ll) amidinates (cf. Schemes 48 and and the mono... 

Polylactide (PLA)-CaS04 composites toughened with low molecular weight and polymeric ester-like plasticizers and related performances. European Polymer Journal 44 3842-3852. 

Jensen et al. reported the stereoselective polymerization of D,L-lactide with dibenzyloxidezinc(2,4,6-trimetylphe-nyimidazol-2-ylidene), which was synthesized as shown in Scheme 39.100 Surprisingly, a mixture of the heterocarbene and benzyl alcohol was a better catalyst for polylactide formation than the zinc complex, and unlike 50 the mixture produced heterotactically enriched polylactide. 

Chisholm et al. synthesized organozinc compounds with bulky biphenolates as catalysts for the ring-opening polymerization of lactides.196 The protonolysis of diethyzinc by the biphenols, in the presence of diisopropylmethanol, afforded the polycyclic, trimetallic zinc-di(ethylzinc) pre-catalyst 135, which polymerizes /m -lactide to polylactide, enriched in isi- and. sir-tetrads (Scheme 85). 

Arimura H, Ohya Y, Ouchi T (2005) Formation of core-shell type biodegradable polymeric micelles from amphiphilic poly(aspartic acid)-Wock-polylactide diblock copolymer. Biomacromolecules 6 720-725... 

The neutral fats used in the preparation of the hydrophobic core of the several liposphere-vaccine formulations described here included tricaprin and tristearin, stearic acid, and ethyl stearate. The phospholipids used to form the surrounding layer of lipospheres were egg phosphatidylcholine and dimyristoyl phosphatidylg-lycerol. Polymeric biodegradable lipospheres were prepared from low molecular weight polylactide (PLA) and polycaprolactone-diol (PCL). 

All liposphere formulations prepared remained stable during the 3-month period of the study, and no phase separation or appearance of aggregates were observed. The difference between polymeric lipospheres and the standard liposphere formulations is the composition of the internal core of the particles. Standard lipospheres, such as those previously described, consist of a solid hydrophobic fat core composed of neutral fats like tristearin, whereas, in the polymeric lipospheres, biodegradable polymers such as polylactide or polycaprolactone were substituted for the triglycerides. Both types of lipospheres are thought to be stabilized by one layer of phospholipid molecules embedded in their surface. 

High molecular weight polylactides, 20 298 High molecular weight polymeric... 

Ropson N, Dubois P, Jerome R, Teyssie P (1995) Macromolecular engineering of polylactones and polylactides. 20. Effect of monomer, solvent, and initiator on the ringopening polymerization as initiated with aluminum alkoxides. Macromolecules 28 7589-7598... 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization of Lactides and Glycolides Preparation of Polylactides, Polyglycolide, and Poly(lactide-co-glycolide). 219... 

Much has been written about Cargill Dow LLC s polylactide (PLA) polymer, also known as NatureWorks PLA. PLA is a thermoplastic produced from biomass sugars by fermentation. The fermentation product, lactic acid, is converted into a lactide that is purified and polymerized using a special ring-opening process (18). 

The polymerization of lactones with tin alkoxides is thought to follow the co-ordination-insertion mechanism[77a]. The ring-opening of the monomer proceeds through acyl-oxygen cleavage with retention of the configuration. Tin(IV) complexes have been used to produce predominantly syndiotactic poly((3-hy-droxybutyrate) [78,79],macrocyclic poly((3-hydroxybutyrate) [80],poly(e-CL), and polylactide [77,76,81]. 

The most efficient way of preparing polylactides is ROP by coordination initiators [132]. This method usually allows a controlled synthesis leading to quite a narrow MWD. Polymerization of the different stereoforms results in materials with different properties. The polymers derived from the pure L-FA or D-FA... 

Keywords Carbon dioxide and epoxides copolymerization Group 13 metal catalysts Group 3 metal catalysts Lactide polymerization Polycarbonate Polylactide... 

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). 

The most effective, and commercially applied, method to produce polylactide is via the ring-opening polymerization of lactide. This process is initiated by metal complexes and proposed to occur via a coordination-insertion mechanism, as illustrated in Fig. 2. The most common initiators for this polymerization are Lewis acidic metal alkoxide or amide complexes. Key initiator criteria are sufficient Lewis acidity to enable binding and activation of the lactide unit and a labile metal alkoxide (or amide) bond so as to enable efficient insertion. 

Narrow distribution in the backbone length as well as in the chemical composition or the branch frequency may be expected from a living-type copolymerization between a macromonomer and a comonomer provided the reactivity ratios are close to unity. This appears to have been accomplished to some extent with anionic copolymerizations with MMA of methacrylate-ended PMMA, 29, and poly(dimethylsiloxane) macromonomers, 30, which were prepared by living GTP and anionic polymerization, respectively [50,51]. Recent application [8] of nitroxide (TEMPO)-mediated living free radical process to copolymerizations of styrene with some macromonomers such as PE-acrylate, la, PEO-methacr-ylate, 27b, polylactide-methacrylate, 28, and poly(e-caprolactone)-methacrylate, 31, may be a promising approach to this end. 

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