A literature review is presented regarding the synthesis, and physicochemical, chemical, and mechanical properties of poly(lactic acid)(PLA). Poly(lactic acid) exists as a polymeric helix, with an orthorhombic unit cell. The tensile properties of PLA can vary widely, depending on whether or not it is annealed or oriented or what its degree of crystallinity is. Also discussed are the effects of processing on PLA. Crystallization and crystallization kinetics of PLA are also investigated. Solution and melt rheology of PLA is also discussed. Four different power-law equations and 14 different Mark–Houwink equations are presented for PLA. Nuclear magnetic resonance, UV–VIS, and FTIR spectroscopy of PLA are briefly discussed. Finally, research conducted on starch–PLA composites is introduced.

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A Literature Review of Poly(Lactic Acid)

4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

Polylactic acid is proving to be a viable alternative to petrochemical-based plastics for many applications It is produced from renewable resources and is biodegradable, decomposing to give H2O, CO2, and humus, the black material in soil In addition, it has unique physical properties that make it useful in diverse applications including paper coating, fibers, films, and packaging (see Figure)

Polylactic Acid Technology

s, and 360 patents, and edited 12 books. He has also received over 80 major awards including the Gairdner Foundation International Award, Lemelson-MIT prize, ACS’s Applied Polymer Science and Polymer Chemistry Awards, AICHE’s Professional Progress, Bioengineering, Walker and Stine Materials Science and Engineering Awards. In 1989, Dr. Langer was elected to the Institute of Medicine of the National Academy of Sciences, and in 1992 he was elected to both the National Academy of Engineering and the National Academy of Sciences. He is the only active member of all three National Academies. Kevin Shakesheff was born in Ashington, Northumberland, U.K., in 1969. He received his Bacheclor of Pharmacy degree from the University of Nottingham in 1991 and a Ph.D. from the same institution in 1995. In 1996 he became a NATO Postdoctoral Fellow at MIT, Department of Chemical Engineering. He is currently an EPSRC Advanced Fellow at the School of Pharmaceutical Sciences, The University of Nottingham. His research group investigates new methods of engineering polymer surfaces and the application of these engineered materials in drug delivery and tissue engineering. 3182 Chemical Reviews, 1999, Vol. 99, No. 11 Uhrich et al.

Polymeric Systems for Controlled Drug Release

RGD modified polymers: biomaterials for stimulated cell adhesion and beyond

PROBLEM TO BE SOLVED: To obtain a conjugate fiber having a good touch and an excellent tensile strength and useful for woven or knitted fabrics, etc., by subjecting the skin layer of a specific conjugate fiber to a weight-reducing treatment. SOLUTION: This conjugate fiber is obtained by feeding a melted aromatic- containing polyester from an extruder into the core line-forming space, feeding the melted product of an aliphatic polyester selected from polybutylene succinate, poly-L-lactic acid or their copolymer into the skin layer-forming space of the nozzle, continuously spinning the core line comprising the aromatic- containing polyester and the skin layer comprising the aliphatic polyester, and subsequently bringing the obtained conjugate fiber into contact with an enzyme such as a lipase or a proteinase-K to reduce the aliphatic polyester constituting the skin layer. The nozzle has the core line-forming space on the inside of the nozzle, and the skin layer-forming space on the outside of the core line- forming space.

Conjugate fiber and its production

PURPOSE:To produce a composition having improved antistatic properties, by introducing previously a quaternary ammonium ion structure component to at least one component, blending a polyalkylene oxide-containing block copolymer with an organic polymer. CONSTITUTION:A composition comprising (A) a block copolymer obtained by adding 10-90wt% polyalkylene oxide compound containing one or more (preferably two) ester- or amide-forming groups during synthesis of a polyester, etc. and (B) an organic polymer such as BET, nylon, etc., obtained by introducing previously an ammonium structure to a polyalkylene oxide chain of the component A, or by using a compound having an ammonium structure as a copolymerizable component of the component A or the component B, introducing a quaternary ammonium ion structure component to at least one of the components A and B, followed by blending the component A with the component B. Preferably the composition contains >=1wt% polyalkylene oxide segment and >=50 equivalents/ton quaternary ammonium ion.

Preparation of antistatic polymer composition

Review: Block copolymers create various types of nanostructures, e.g., spheres, rods, cubes, and lamellae. This review discloses the dynamic macromolecular organization of block copolymers comprising poly(L-lactide) (PLLA) and poly(oxyethylene) (PEG) that allows to simulate elaborate biological systems. The block copolymers, AB- (PLLA-PEG) and ABA-type (PLLA-PEG-PLLA), are synthesized by ordinary lactide polymerization to have a controlled block length. They are dispersed into an aqueous medium to prepare nano-scale particles, consisting of hydrophobic PLLA and hydrophilic PEG in the core and shell, respectively. Then, the particles are placed on a flat substrate by the casting method. The particles are detected as discoids by AFM, having shrunk with loss of water. Heat-treatment of these particles at 60 °C (above T g of PLLA) gives rise to a collapse into small fragments, which then aggregate into bands with nano-size width and thickness. The PLLA-PEG bands align parallel to each other, while the PLLA-PEG-PLLA bands form a characteristic network resembling the neuron system created in animal tissue. As analyzed by TEM diffraction, each is composed of α-crystal of PLLA whose c-axis (molecular axis) is perpendicular to the substrate surface. Based on this fact, a doubly twisted chain structure of PLLA is proposed in addition to a plausible mechanism for the self- organization of the block copolymers. Derivatives of the PLLA-PEG block copolymers can form far more interesting nano-architectures. An equimolar mixture of enantiomeric copolymers, PLLA-PEG-PLLA and PDLA-PEG- PDLA, forms a hydrogel that is thermo-responsive. The terminal-modified poly(L-lactide)-block-polyoxyethylene monocinnamate (PLLA-PEG-C) forms a highly stabilized nanofiber by the photo-reaction of the cinnamates placed in the outer layer of the nanobands.

Macromolecular organization of poly(L-lactide)-block-polyoxyethylene into bio-inspired nano-architectures

Silicon monoxide (SiO) amorphous layer was deposited on the biaxially oriented nylon 6 films in a vacuum evaporator. This deposited layer tightly attaches to the nylon film. SiO deposited nylon 6 films thus obtained are transparent and show a high barrier to the water vapor and oxgen. Wettability of the SiO surface of the film to the water, ink, and the adhesives are satisfactory for the gravure printing and lamination with polyolefin films. It was found that the gloss of nylon film, which reflects the surface roughness of the film, affects the uniformity of SiO deposited layer on the nylon film and barrier property of the deposited films. Permeabilities of the water vapor and oxygen through the SiO deposited nylon films were fairly high just after the deposition, especially when the deposited layer was thin, and then decreased to lower equilibrium values. These equilibrium values are surprisingly low comparing with other high barrier films such as nylon and polypropylene films coated with poly (vinylidene chloride). Further the SiO vacuum deposition was continuously carried out on the running nylon film. We found that the thickness of the silicon oxide layer on the nylon film and the water permeability are strongly related to the running velocity of the nylon film and the applied electric current to the heater.

Yoshiharu Kimura

Papers

Conjugate fiber and its production

Preparation of antistatic polymer composition

Macromolecular organization of poly(L-lactide)-block-polyoxyethylene into bio-inspired nano-architectures

Vacuum deposition of Silicon oxide on the nylon 6 films utilizing silicon monooxide as an evaporation material

Studies on the Hydrous Niobium(V) Oxide Ion Exchanger. Part 1.