Norioki Kawasaki

Novel star-shaped polylactide with glycerol using stannous octoate or tetraphenyl tin as catalyst: 1. Synthesis, characterization and study of their biodegradability

Abstract Novel star-shaped polyesters were synthesized by reacting l -lactide (LLA) with glycerol (GL) in the presence of stannous octoate or tetraphenyltin as catalyst. These polymers were characterized by nuclear magnetic resonance, Fourier-transform infra-red spectroscopy, differential scanning calorimetry (d.s.c.) and thermogravimetric analysis. D.s.c. curves showed that these polymers are semicrystalline when the ratio LLA/GL is higher than 20/1 (mol/mol). When this molar ratio falls below 20/1, the polymers are amorphous. The molecular-weight distribution of these polymers was studied with gel permeation chromatography measurements, which showed that the M n decreased proportionally to the glycerol content in the polymer. The potential biodegradability of these polymers was assessed with the aid of enzymatic and alkali hydrolysis.

Production of N-acetyl-D-glucosamine from α-chitin by crude enzymes from Aeromonas hydrophila H-2330

The selective and efficient production of N-acetyl-D-glucosamine (GlcNAc) was achieved from flake type of alpha-chitin by using crude enzymes derived from Aeromonas hydrophila H-2330.

Enzymatic production of N-acetyl-D-glucosamine from chitin. Degradation study of N-acetylchitooligosaccharide and the effect of mixing of crude enzymes

N-Acetyl-D-glucosamine (GlcNAc) was produced from chitin by use of crude enzyme preparations. The efficient production of GlcNAc by cellulases derived from Trichoderma viride (T) and Acremonium cellulolyticus (A) was observed by HPLC analysis compared to lipase, hemicellulase, and pectinase. b-Chitin showed higher degradability than a-chitin when using cellulase T. The optimum pH of cellulase T was 4.0 on the hydrolysis of b-chitin. The yield of GlcNAc was enhanced by mixing of cellulase T and A. q 2003 Elsevier Science Ltd. All rights reserved.

Synthesis and degradability of a novel aliphatic polyester based on l-lactide and sorbitol: 3

Abstract Reaction of L -lactide (LLA) with sorbitol (SB) in the presence of stannous octoate (Sn oct), tetraphenyl tin (TPhT) and several other catalysts gave a series of novel polyesters. Several techniques such as nuclear magnetic resonance (n.m.r.) and Fourier transform infra-red ( FT i.r.) spectroscopy, gel permeation chromatography (g.p.c.) and differential scanning calorimetry (d.s.c.) were used in order to characterize these polymers. The crystallinity of the polyesters was found to depend on the molar ratio of LLA to SB, i.e. when LLA/SB > 20/1 or > 40/1 (for Sn oct or TPhT, respectively) the polyesters are semicrystalline (from d.s.c. results) whereas at molar ratios of LLA to SB which are lower than those mentioned above the polymers become amorphous. High SB contents have an adverse effect on the thermal properties (i.e. lower T g , T m , and ΔH m ) and the molecular weight distribution (lower M n , and M w ) but they enhance their biodegradability. The latter was tested in terms of enzymatic and alkali hydrolysis. Both total organic carbon (TOC) and g.p.c. measurements confirmed the degradation of the polyesters at different hydrolysis modes.

Ring-opening copolymerization of succinic anhydride with ethylene oxide initiated by magnesium diethoxide

Abstract The ring-opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO) was carried out by using mainly magnesium diethoxide (ME) as an initiator. ME was superior with respect to polymerization yield and number-average molecular weight (Mn) of the copolymers obtained. The copolymers were found to be alternating copolymers independent of feed monomer molar ratio. The yield and the Mn of the copolymers increased with the polymerization temperature and the time within 48 h. There was a maximum of Mn at a time of 48 h, at 100°C. The Mn of the alternating copolymers was as high as 1.3 × 104. The Mn of the copolymers increased proportionally with the increase of monomer/initiator molar ratio (M/I) up to M/I = 400. From analysis of the end-groups of low Mn of copolymers by 1H n.m.r., these copolymers were a mixture of two copolymers having different end groups. One had ethyl ester group connecting with SA at either end group, the other had ethyl ester group connecting with SA and hydroxyl group connecting with EO.

Chemical modification of chitosan. Part 15: Synthesis of novel chitosan derivatives by substitution of hydrophilic amine using N-carboxyethylchitosan ethyl ester as an intermediate

The Michael type reaction of chitosan with ethyl acrylate has been investigated. Although this reaction was quite slow in the case of chitosan, the reiteration of the reaction was an effective means for increasing the degree of substitution (DS) of ethyl ester. The N-carboxyethylchitosan ethyl ester as an intermediate was successfully substituted with various hydrophilic amines, although the simultaneous hydrolysis of the ester to carboxylic acid also occurred. Water-soluble chitosan derivatives were obtained by substitution with hydroxyalkylamines and diamines.

Study of biodegradability of poly(δ-valerolactone-co-L-lactide)s

The biodegradability of poly(δ-valerolactone-co-L-lactide)s was studied both with enzymatic (lipase from Rhizopus arrhizus) and nonenzymatic hydrolyses. The hydrolyzability was evaluated by recording the amount of the hydrolyzed water-soluble products. The enzymatic hydrolysis was considerably affected by copolymer composition. The copolyester, the most susceptible to enzymatic hydrolysis, was the one containing a 90 mol % δ-valerolactone unit. The copolymers were also nonenzymatically hydrolyzed at 70°C. The results were similar to those of enzymatic hydrolysis, confirming the influence of copolymer composition on the hydrolyzability. However, the L-lactide rich copolymers were more susceptible to hydrolysis. These results suggest that poly(δ-valerolactone) is easily degraded by lipase, whereas poly(L-lactide) is degraded through simple hydrolysis.

Synthesis and degradability of a novel aliphatic polyester : poly(β-methyl-δ-valerolactone-co-L-lactide)

Biodegradable polyesters were synthesized by ring-opening copolymerization of L-lactide (LA) with DL-β-methyl-δ-valerolactone (MV). 1H and 13C nuclear magnetic resonance analyses showed that these copolymers were statistical and that their number-average molecular weights were within the range of (3–5) × 104. The melting temperatures of these polyesters were dependent upon the LA content in the copolymers, thus showing that high LA composition resulted in higher Tm. The copolymers containing more than 90 mol% LA formed tough and hard films, whereas those with less than 80 mol% LA formed flexible films similar to natural rubber. Accelerated hydrolysis was carried out with copolymers of various compositions at 70°C for 18 days. The hydrolysis rates were much faster than that of poly(LA), which is well known to be a hydrolysable polymer. The copolymers were easily hydrolysed with lipases from Rhizopus arrhizus, R. delemar, Pseudomonas sp. and Candida cylindracea. In particular, the lipases from R. arrhizus and R. delemar proved to be very effective in promoting hydrolysis.

Synthesis and characterization of novel biodegradable copolyesters by transreaction of poly(ethylene terephthalate) with copoly(succinic anhydride/ethylene oxide)

Poly(ethylene terephthalate)/copoly(succinic anhydride/ethylene oxide) copolymers, (PET/PES copolymers) were synthesized by the transreaction between PET and PES and characterized with GPC, 1 H NMR, and DSC. Most of the copolymers obtained were random copolymers. The films cast of these copolymers were transparent. The thermal, mechanical properties, and biodegradability of the copolymers obtained were studied with respect to the composition and lengths of aliphatic and aromatic units in the copolymers. In the copolymers having high PET content, the melting points, due to the PET segment, were observed by DSC measurement, although the fusion heats of the copolymers were small. The enzymatic hydrolyzability by a lipase from Rhizopus arrhizus and biodegradability by activated sludge of the copolymers decreased with an increase in PET content. When the length of succinic acid unit in the copolymer was below 2, the hydrolyzability of the copolymers decreased considerably. The tensile strengths of the cast films prepared from the copolymers synthesized by the transreaction increased with an increase in PET content, whereas, the elongations at break decreased. Their tensile strengths were half, and the elongations were double compared to those of PET homopolymer film.

Synthesis and biodegradability of novel copolyesters containg γ-butyrolactone units

Abstract Copolymers were synthesized by ring-opening polymerization of γ-butyrolactone (BL) with cyclicesters. Comonomers used were l -lactide (LLA), glycolide (GL), β-propiolactone (PL), δ-valerolactone (VL) and e-caprolactone (CL). Tetraphenyl tin was used as an initiator. The copolymerization was carried out in bulk at 140°C for 4 days and the polymers were characterized by 1H n.m.r., 13C n.m.r., g.p.c. and d.s.c. The BL contents of the copolymers varied in the range 0 and 26 mol%. The number average molecular weights were from 1.3 × 103 to 1.5 × 105. When a small amount of the BL unit was introduced into the polymer chain, increased flexibility and excellent biodegradability were imparted to the polymer. However, excess of BL resulted in low molecular weight polymers with substantially low yields. D.s.c. measurements showed that the copolymers had one single endothermic peak at lower temperatures than those of the Tms of each homopolymer. The BL rich copolymers were shown to be amorphous. The statistical nature of the synthesized copolymers was confirmed with n.m.r. analysis. The copolyesters were hydrolyzed in distilled water at 70°C and their hydrolyzability was found to be affected by the chemical structure and polymer composition. The hydrolyzability of glycolide or lactide copolymers was high in comparison with other copolyesters. The BL-rich copolyesters were easily hydrolyzed. The copolymers were also hydrolyzed with lipases from Rhizopus arrhizus, R. delemar and Candida cylindracea in phosphate buffer solution (pH 7.0) at 37°C. Copolymers without substituents, such as the poly(BL-co-e-caprolactone)s, were easily enzymatically hydrolyzed. It is noteworthy that the non-enzymatic hydrolysis was not affected by the presence of substituents.