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

This article attempts to bring together basic and complex information which has been gathered on cellulose structure, principally that of native cellulose, over the last few decades. Even though advances have been made in the field of crystallography, powder crystallography cannot yield a definitive cellulose structure and single crystal diffraction is not possible due to the lack of suitable crystals. Knowledge obtained on the biosynthesis of native cellulose and on the polymorphy of cellulose and its derivatives help our understanding of ultrastructure. Many inconsistencies between early crystallographic studies of native cellulose have been clarified by the discovery that two polymorphs (α and β) of cellulose I exist. Models of the possible ultrastructural arrangements within native cellulose have been put forward over the decades; with advancement in technology, computer simulations of small and large systems are being created to test the viability of these ultrastructural models. It is hoped that this review will aid in the understanding of the complexity and uncertainties that still exist in this subject

Cellulose: the structure slowly unravels

Summary: Poly(lactide)s [i.e. poly(lactic acid) (PLA)] and lactide copolymers are biodegradable, compostable, producible from renewable resources, and nontoxic to the human body and the environment. They have been used as biomedical materials for tissue regeneration, matrices for drug delivery systems, and alternatives for commercial polymeric materials to reduce the impact on the environment. Since stereocomplexation or stereocomplex formation between enantiomeric PLA, poly(L-lactide) [i.e. poly(L-lactic acid) (PLLA)] and poly(D-lactide) [i.e. poly(D-lactic acid) (PDLA)] was reported in 1987, numerous studies have been carried out with respect to the formation, structure, properties, degradation, and applications of the PLA stereocomplexes. Stereocomplexation enhances the mechanical properties, the thermal-resistance, and the hydrolysis-resistance of PLA-based materials. These improvements arise from a peculiarly strong interaction between L-lactyl unit sequences and D-lactyl unit sequences, and stereocomplexation opens a new way for the preparation of biomaterials such as hydrogels and particles for drug delivery systems. It was revealed that the crucial parameters affecting stereocomplexation are the mixing ratio and the molecular weight of L-lactyl and D-lactyl unit sequences. On the other hand, PDLA was found to form a stereocomplex with L-configured polypeptides in 2001. This kind of stereocomplexation is called “hetero-stereocomplexation” and differentiated from “homo-stereocomplexation” between L-lactyl and D-lactyl unit sequences. This paper reviews the methods for tracing PLA stereocomplexation, the methods for inducing PLA stereocompelxation, the parameters affecting PLA stereocomplexation, and the structure, properties, degradation, and applications of a variety of stereocomplexed PLA materials.

http://www.mate.tue.nl/~peters/WimBras/LuigiBalzano/2011_03_11%20LB/Tsuji%20StereoComplex.pdf

Poly(lactide) Stereocomplexes: Formation, Structure, Properties, Degradation, and Applications

The entanglement concept in polymer rheology

Chitin and chitosan, typical marine polysaccharides as well as abundant biomass resources, are attracting a great deal of attention because of their distinctive biological and physicochemical characteristics. To fully explore the high potential of these specialty biopolymers, basic and application researches are being made extensively. This review deals with the fundamental aspects of chitin and chitosan such as the preparation of chitin and chitosan, crystallography, extent of N-acetylation, and some properties. Recent progress of their chemistry is then discussed, focusing on elemental modification reactions including acylation, alkylation, Schiff base formation and reductive alkylation, carboxyalkylation, phthaloylation, silylation, tosylation, quaternary salt formation, and sulfation and thiolation.

Chitin and Chitosan: Functional Biopolymers from Marine Crustaceans

This paper describes a novel method to determine the degree of deacetylation of chitosan by 1H NMR spectroscopy. Measurements were carried out at 70°C by using 2 wt% CD3COOD/D2O and 2 wt% DC1/D2O as solvents for chitosan. In the case of DC1/D2O system, effect on hydrolysis of chitosan should be taken into consideration, and the pulse repetition delay required for 45° pulse is 40s. Whereas, in regard to CD3COOD/D2O system, 6s pulse repetition delay is enough for 45° pulse, and moreover, high magnetic field NMR apparatus is necessary, because signal of CD2H residue in CD3COOD overlaps with that of CH3 residue in N-acetyl residue and determination of the difference of two spectra is required. The proposed method is more effective, precise and simple, comparing with the conventional colloid titration and elemental analysis methods. Assignments of 1H and 13C NMR spectra of chitosan are also reported.

Determination of degree of deacetylation of chitosan by 1H NMR spectroscopy

The solid state 13 C NMR spectrum of the stereocomplex (D1L1P) prepared from poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) in a dilute acetonitrile solution exhibits three resonance lines I-III appear at 173.3, 172.0,and 169.7 ppm respectively, for the carbonyl carbons of DILIP. Line I is further resolved into two components which can be assigned to the rigid and disordered racemic crystalline components, respectively. Line II is the contribution from the noncrystalline region; where the segments of PDLA and PLLA may be almost randomly mixed

Stereocomplex formation between enantiomeric poly(lactic acid)s. 7. Phase structure of the stereocomplex crystallized from a dilute acetonitrile solution as studied by high-resolution solid-state carbon-13 NMR spectroscopy

Structural changes of native cellulose crystals induced by annealing in aqueous alkaline and acidic solutions at high temperatures

Cross polarization/magic angle spinning 13C n.m.r. study of solid structure and hydrogen bonding of poly(vinyl alcohol) films with different tacticities

Hisashi Odani

Papers

Determination of degree of deacetylation of chitosan by 1H NMR spectroscopy

Stereocomplex formation between enantiomeric poly(lactic acid)s. 7. Phase structure of the stereocomplex crystallized from a dilute acetonitrile solution as studied by high-resolution solid-state carbon-13 NMR spectroscopy

Structural changes of native cellulose crystals induced by annealing in aqueous alkaline and acidic solutions at high temperatures

Cross polarization/magic angle spinning 13C n.m.r. study of solid structure and hydrogen bonding of poly(vinyl alcohol) films with different tacticities

Successive differential absorptions of vapors by glassy polymers