D-lactide

The phase space of the poly(ethylene-aft-propylene)-fr-poly(d, (-lactide) (PEP-fo-PLA) system was recently explored by Schmidt and Hillmyer [63]. All equilibrium symmetries I, C, S, and G were observed. The G morphology, however, existed in only a small region between the L and C in close proximity to the ODT (Fig. 12). 

Lactide (LA), the cyclic diester of lactic acid, has two stereogenic centers and hence exists as three stereoisomers L-lactide (S,S), D-lactide (R,R), and meso-lactide (R,S). In addition, rac-lactide, a commercially available racemic mixture of the (R,R) and (S,S) forms, is also frequently studied. PLA may exhibit several stereoregular architectures (in addition to the non-stereoregular atactic form), namely isotactic, syndiotactic, and heterotactic (Scheme 15). The purely isotactic form may be readily prepared from the ROP of L-LA (or D-LA), assuming that epimerization does not occur during ring opening. The physical properties, and hence medical uses, of the different stereoisomers of PLA and their copolymers vary widely and the reader is directed to several recent reviews for more information.736 740-743... 

Usual PLAs have two enatiomeric forms, PLLA and poly(D-lactide) (PDLA), which are synthesized from LLA and the D,D-isomer of lactide (DLA), respectively. It is well known that 1 1 mixture of PLLA and PDLA can form a stable stereocomplex (SC), which has a higher Tm and higher mechanical strength than either of homopolymers [261], We reported on the utility of SC formation to enhance the stability of nanogels. Monodisperse SC nanogels were obtained through the self-assembly of an equimolar mixture of Dex-g-OLLA and Dex-g-ODLA in a dilute aqueous solution. 

Spassky and coworkers discovered a remarkable stereocontrol of an enantiomerically pure A1 complex (7 )-161a for the ROP of rac-lactide resulting in a tapered stereoblock PLA microstructure with high melting point =187 °C) (Fig. 26) [160]. Structurally analogous, racemic salen-Al complex 162 resulted in highly isotactic PLA [161]. Feijen s enantiopure chiral complex (RJ )-163 (Fig. 26) exhibited an excellent reverse stereocontrol by preferential polymerization of L-lactide over D-lactide monomer (Kss/Krr = 14) that resulted in PLA with... 

In addition to lactones, lactides and glycolides are highly interesting monomers for evaluation in lipase-catalyzed ROP. Lactide is the cyclic dimer of lactic acid and can occur in three stereo-configurations L-lactide, D-lactide, and D,L- or meso-lactide (Fig. 6). In analogy, glycolide is the cyclic dimer of glycolic acid but is... 

The conformations of stereoregular poiyIL-lactide and regularly alternating polyiL.D-lactide) confined to occupy cylinders of varying radii are determined in an effort to learn if either polylactide could be incorporated in the narrow channels of its inclusion compound with urea. 

Fig. 9. Structure of the different stereoforms of the lactide monomer and the resulting repeating unit, the chiral center marked with. a) l-LA, b) D,D-lactide, and c) meso-lactide...

Meikle, M.C. Papaioannou, S. Ratledge, T.J. Speight, P.M. Watt-Smith, S.R. Hill, P.A. Reynolds, J.J. Effect of poly D-lactide-co-glycolide implants and xenogeneic bone matrix-derived growth factors on calvarial bone repair in the rabbit. Biomaterials 1994, 15 (7), 513-521. 

Poly(D-lactide) 100 0 0 d-PLA Purasorb PD PURAC (3/ -cis)-3,6-Dimethyl-l, 4-dioxane-2,5-dione homopolymer [25038-75-9]... 

Random copolymerization of MMA with other polar monomers proceeds in a living fashion with relative monomer reactivity ratios in the order BuA > MMA = EtMA > /-PrMA when mediated by 4(Sm Me)/THF [60, 89]. Block polymerization of MMA with other polar monomers as lactone yields ideal living copolymers (PDI = 1.11-1.34) under these conditions. Similarly, ABA triblock copolymers were obtained by sequential addition of MMA, BuA, and MMA [89]. AB block copolymers could be obtained by sequential addition of (L,L)-lactide and (D,D)-lactide (PDI = 1.38) as well as -caprolactone and (l,l)- lactide monomers (PDI = 1.36) in the presence of Y(OCH2CH2NMe2) [82]. 

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