Lactide Polymers

Lactic acid and levulinic acid are two key intermediates prepared from carbohydrates [7]. Lipinsky [7] compared the properties of the lactide copolymers [130] obtained from lactic acid with those of polystyrene and polyvinyl chloride (see Scheme 4 and Table 5) and showed that the lactide polymer can effectively replace the synthetics if the cost of production of lactic acid is made viable. Poly(lactic acid) and poly(l-lactide) have been shown to be good candidates for biodegradeable biomaterials. Tsuji [131] and Kaspercejk [132] have recently reported studies concerning their microstructure and morphology. 

Table 5 Comparison of Properties of Lactide Polymers with Polystyrene and Poly(vinyl chloride) ...

Bandyopadhyay, S., Chen, R. and Giannelis, E.P. 1999. Biodegradable organic-inorganic hybrids based on poly(L-lactide). polymer material science engineering 81 159-160. 

Kulinski, Z. and Piorkowska, E. 2005. Crystallization, structure and properties of plasticized poly(L-lactide). Polymer 46 10290-10300. 

Reservoir or coaxial fibers can be produced from the glycolide/ lactide polymers (53,55). Two different methods have been investigated. Dunn (53) utilized a melt-spinning technique in which the drug was introduced during the spinning process as a suspension or solution in a suitable lumen fluid. Eenink (55) developed a dry-... 

A human contraceptive vaccine based on lactide polymers is currently being developed. The antigen is a 37-amino-acid peptide of B-HCG conjugated to diphtheria toxoid. The antigen is administered wtih microencapsulated muramyl dipeptide as an adjuvant. Studies in rabbits have shown 9-12 months of elevated antibody liter following... 

Lactide polymers, manufacture of, 14 122 Lactisole, 24 246 Lactitol, 12 40 Lactobacillic acid, 5 36t Lactobacillus, 12 478 Lactococcus, 12 478 Lactoferrins, 18 258 Lactones, 10 497 12 663-664 aroma chemicals, 3 256 in beer, 3 582t Lactonitrile, 8 174 Lactonization, 10 499... 

Gruber PR, Hall ES, Kolstad JJ, Iwen ML, Benson RD, Borchardt RL (1994) Continuous process for manufacture of lactide polymers with purification by distillation. US Patent 5357035... 

Sosnowski et al. [124,125] have reported that uniform biodegradable polymeric particles with diameters of less than 5 pm can be prepared by ringopening dispersion polymerization of L,L-lactide in heptane-dioxane mixed solvent in the presence of poly(dodecyl acrylate)-g-poly( -caprolactone), which were synthesized by copolymerization of dodecyl acrylate with poly(e-caprolactone) macromonomers, 46. It is noted that the polymer particles consist of well-defined poly(L,L-lactide) polymers with Mn lxl04 and Mw/Mn 1.06. 

When using the aluminium isopropoxide catalyst to promote the polymerisation of lactide, all three isopropoxide groups have been found to initiate the polymerisation [137,139]. Ring cleavage in the polymerisation with aluminium isopropoxide and diethylaluminium isopropoxide occurred at the C(0)-0 bond, leading to aluminium alcoholate propagating species [139], Lactide polymerisation with other catalysts containing multinuclear species proceeded similarly [138-140]. Analysis of stereosequences of lactide polymers obtained with catalysts such as aluminium isopropoxide, diethylaluminium alcoholate and methylaluminoxane indicates that none of these catalysts favours the formation of isotactic blocks [139]. 

Poly(e-caprolactone) (PCL) is synthesized by anionic, cationic or coordination polymerization of e-caprolactone. Degradable block copolymers with polyethylene glycol, diglycolide, substituted caprolactones and /-valerolactone can also be synthesized. Like the lactide polymers, PCL and its copolymers degrade both in vitro and in vivo by bulk hydrolysis, with the degradation rate affected by the size and shape of the device and additives. 

NatureWorks LLC has set up a 300 million plant at Blair, NE, which is capable of producing about 140,000-tons/year of poly-lactide polymers from com sugar. It employs a fermentation process to produce two chiral isomers of lactic acid from glucose, which are then cracked to form three lactide isomers. The isomers are subsequently polymerized to polylactide. 

Turning the lactic acid into a polymer involves a chemical process called condensation, whereby two lactic acid molecules are converted into one cyclic molecule called a lactide. This lactide is purified through vacuum distillation. A solvent-free melt process causes the ring-shaped lactide polymers to open and join end-to-end to form long chain polymers. A wide range of products that vary in molecular weight and crystallinity can be produced, allowing the PLA to be modified for a variety of applications. 

Yeh, M. K. (2000), The stability of insulin in biodegradable microparticles based on blends of lactide polymers and polyethylene glycol,/. Microencapsul., 17, 743-756. 

Gruber P. Kolstad J. Ryan C. Hall E. Eichen R. US Patent 5484881 Melt stable amorphous lactide polymer film, 1996. 

P. Gruber, E. Hall, J. Kolstad, M. Iwen, R. Benson, and R. Borchardt, Continuous process for manufacture of lactide polymers with controlled optical purity US 5,142,023, assigned to Cargill, Incorporated (Minnetonka, MN), 1992. 

More recent work on compoimd vascular grafts has focused laigely on the incorporation of lactide polymers. An early report came from Ruderman s group at Walter Reed. They evaluated woven grafts composed of 24% PLLA and 76% Dacron implanted into the abdominal aorta of dogs. After 100 days, they foimd all grafts to be patent with extensive tissue ingrowth. ... 

Auras, B. R. A., Singh, S. R, Singh, J. J. Evaluation of oriented poty (lactide) polymers vs. Existing PET and oriented PS for fresh food service containers packaging technology and science. 

Tsuji, H. and Ikada, Y. (1995) Properties and morphologies of poly(L-lactide) 1. Annealing condition effects on properties and morphologies of poly(L-lactide). Polymer, 36,2709-2716. 

Sodergard, A., Selin, J.F. and Nasman, J.H. (1996) Hydrolytic degradation of peroxide modified poly(L-lactide). Polymer Degradation and Stability, 51,351-359. 

Hyon, H., Jamshidi, K. and Ikada, Y. (1998) Effects of residual monomer on the degradation of DL-lactide polymer. Polymer International, 46,196-202. 

Schwach G., Coudane J., Engel R., Vert M., Stannous octoate-versus zinc-initiated polymerization of racemic lactide, Polym. Bull., 32, 1994, 617-623. 

Puiggali J., Ikada Y., Tsuji H., Cartier L., Okihara T., Lotz B., The frustrated structure of polyfL-lactide), Polymer, 41, 2000, 8921-8930. 

Zhang X., Wyss U.P., Pichora D., Goosen M.F.A., An investigation of the synthesis and thermal stability of poly(DL-lactide), Polym. Bull, 27, 1992, 623-629. 

DD and LL pair linkages during the ring-opening polymerization of racemic lactide. /. Polym. ScL, Part A Polym. Chem., 35 (9), 1651-1658. 

Ghobadi, E, Heuchel, M., Kratz, K., and Lendlein, A. (2013) Influence of the addition of water to amorphous switching domains on the simulated shape-memory properties of poly(L-lactide). Polymer, 54 (16), 4204 -4211. 

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