Polymers polylactides

The second concept for the generation of monolithic polymers is based on diblock copolymers which were prepared by Hillmyer and coworkers [27]. These copolymers contain oriented nanoscopic cylinders of the degradable polymer polylactide (PLA) which were embedded in polystyrene. The latter served as an inert thermoplastic matrix, while PLA could be selectively removed under well-defined conditions using sodium hydroxide in aqueous methanol. The resulting mesoporous monolithic polystyrene contains nanochannels with defined pore size. The major drawback of this material free of any cross-linker is associated with reduced mechanical and chemical stability. 

One of the most studied blends has been the one composed of P(3HB) and polylactide, both commercially available polymers with superior thermal and mechanical properties than other commercial polymers. Polylactide is a chemically synthesized, biodegradable thermoplastic and derived from renewable resources. It has been shown that this blend exhibited greater flexibility and hydrolytic biodegradation than the Polylactide or P(3HB) alone [75]. 

Stoclet, G., Seguela, R., and Lefebvre, J.M. (2011) Morphology, thermal behavior and mechanical properties of binary blends of compatible biosourced polymers Polylactide/polyamidell. Polymer, 52, 1417-1425. 

The polymer polylactide (PEA) is another polyester. Although not made from any auto-oxidation product, we discuss it here because in recent years it has come under much attention. As mentioned in Section 1.6.3, lactic acid is a fermentation product, and, unlike PET, PEA is biodegradable. 

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). 

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... 

Jacobsen, S. and Fritz, H.G. 1999. Plasticizing polylactide, the effect of different plasticizers on the mechanical properties. Polymer Engineering and Science 39 1303-1310. 

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

Takagi, Y., Yasuda, R., Yamaoka, M. and Yamane, T. 2004. Morphologies and mechanical properties of polylactide blends with medium chain length poly(3-hydroxyalkanoate) and chemically modified poly(3-hydroxyalkanoate). Journal of Applied Polymer Science 93 2363-2369. 

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., polyethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

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. 

Carboxylic Acids Obtained by Fermentation of Carbohydrates Lactic (2-hydroxy-propionic) acid obtained by fermentation of glucose and polysaccharides is used by NatureWorks (Cargill/Dow LLC) to prepare polylactide (PLA), a biodegradable or recyclable polymer with a potential production of 140000 t a-1 (Scheme 3.4) [23], This and other potential useful reactions from lactic acid have been reviewed by Datta and Henry [24],... 

Since 1989, Cargill, has invested some 750 million to develop and commercialize polylactic acid (tradename NatureWorks). Its Nebraska plant, with an annual capacity of 140,000 metric tons, opened in 2002. Thus, polylactides, combining favorable economics with green sustainability, are poised to compete in large-volume markets that are now the domain of thermoplastic polymers derived from petrochemical sources. 

One approach to compartmentalize hemoglobin is to encapsulate hemoglobin in biodegradable polymer-PEG-polylactide (30). These nanocapsules have a diameter of 80-150 nm and contain superoxide dismutase, catalase, carbonic anhydrase, and other enzymes of Embden-Meyerhof pathway that are needed for long-term function of an oxygen carrier (31,32). The polylactide capsules are metabolized in vivo to water and carbon... 

---