In-Joo Chin

Biodegradation of poly(3-hydroxybutyrate), Sky-Green® and Mater-Bi® by fungi isolated from soils

In order to characterize the degradation behavior of three commercial biodegradable plastics, poly(3hydroxybutyrate) (PHB), Sky-Green 1 (SG), a biodegradable aliphatic polyester made of succinic acid, adipic acid, butanediol and ethylene glycol, and Mater-Bi 1 (MB), a composite composed of starch based biodegradable polymers, were incubated in the forest soil, in the sandy soil, in the activated sludge soil, and in the farm soil at 28, 37, and 608C, respectively. Seven PHB degrading fungi, five SG degrading fungi, and six MB degrading fungi were isolated by analyzing the microbiological characteristics of the fungi. Biodegradation of all three polymers was most active in the activated sludge soil. Both SG and MB showed higher degradability at 288C than at 378C. Biodegradability of PHB was highest at 378C, while degradation of MB occurred reasonably well at 608C. In the modified Sturm test Penicillium simplicissimum LAR 13 and Paecilomyces farinosus LAR 10 degraded PHB relatively well, while the degradation rate by Aspergillus fumigatus LAR 9 was lower than expected. P. simplicissimum LAR 13 showed the highest degradation rate for SG and A. fumigatus LAR 9 was most eAective in degrading MB. Biodegradability of isolated fungi was aAected by the incubation temperature. In both the soil burial test and the modified Sturm test the order of the biodegradation rate was PHB > SG > MB. 7 2000 Elsevier Science Ltd. All rights reserved.

Crystallization behavior of biodegradable amphiphilic poly(ethylene glycol)‐poly(L‐lactide) block copolymers

Poly(ethylene glycol)-poly(L-lactide) diblock and triblock copolymers were prepared by ring-opening polymerization of L-lactide with poly(ethylene glycol) methyl ether or with poly(ethylene glycol) in the presence of stannous octoate. Molecular weight, thermal properties, and crystalline structure of block copolymers were analyzed by 1H-NMR, FTIR, GPC, DSC, and wide-angle X-ray diffraction (WAXD). The composition of the block copolymer was found to be comparable to those of the reactants. Each block of the PEG–PLLA copolymer was phase separated at room temperature, as determined by DSC and WAXD. For the asymmetric block copolymers, the crystallization of one block influenced much the crystalline structure of the other block that was chemically connected to it. Time-resolved WAXD analyses also showed the crystallization of the PLLA block became retarded due to the presence of the PEG block. According to the biodegradability test using the activated sludge, PEG–PLLA block copolymer degraded much faster than PLLA homopolymers of the same molecular weight.

Crystallization behavior of poly(l-lactide)-poly(ethylene glycol) multiblock copolymers

Abstract Poly( l -lactide) (PLLA)-poly(ethylene glycol) (PEG) multiblock copolymers were synthesized by polyesterification reaction of dicarboxylated PLLA with PEG in the presence of dicyclohexylcarbodiimide and N-dimethylaminopyridine. Dicarboxylated PLLA was prepared by a direct condensation polymerization of l -lactic acid with predetermined amounts of succinic acid, which was used to provide PLLA with a carboxylated terminal group. DSC and X-ray diffractometry of the multiblock copolymer suggested that PLLA and PEG blocks were phase separated and the crystallization behavior of one block was markedly affected by the presence of the other block, and in particular by the block length of the other block. The longer the PLLA block, the lower the crystallinity and the melting temperature of the PEG block. Multiblock copolymers crystallized from the melt and those from the solution casting showed different crystallization behavior, even though the chemical structures and the molecular weights were the same. The crystallizability of the PLLA block was more affected by the crystallization method than that of the PEG block.

Blending of poly(L-lactic acid) with poly(cis-1,4-isoprene)

Abstract Poly( L -lactic acid) (PLLA), a brittle biodegradable thermoplastic polymer, was blended with rubbery poly(cis-1,4-isoprene) (PIP). The PLLA/PIP blend, however, was incompatible as indicated by two T g ’s, each stemming from PLLA and PIP domains, respectively. Since PLLA was known to be compatible with poly(vinyl acetate) (PVAc), PIP was grafted with vinyl acetate monomer to form PIP-g-PVAc, which was then blended with PLLA. The blend of PLLA and PIP-g-PVAc had two T g ’s. The lower T g , which was due to PIP phase, did not vary with the blend composition, while the higher T g , which was due to PLLA rich phase, decreased with an increase in the graft copolymer content. The PVAc moiety of the graft copolymer seems to have been mixed in with PLLA. The tensile properties of the PLLA/PIP-g-PVAc blend were much superior to those of the PLLA/PIP blend.

Effect of poly(ethylene glycol)-block-poly(L-lactide) on the poly[(R)-3-hydroxybutyrate]/poly(L-lactide) blends

Abstract Compatibility of the poly[(R)-3-hydroxybutyrate] (PHB)/poly( L -lactide) (PLLA) blend was investigated, with and without compatibilizer. PHB and PLLA were shown to be compatible, as long as the molecular weight of PLLA was 11,700 g/mol or less. However, when the molecular weight of PLLA was 56,000 (56K) or 190,000 (190K) g/mol, PLLA was incompatible with PHB. Mechanical properties of the PHB/56K PLLA blends containing PEG-b-PLLA copolymer or PVAc as compatibilizer were not improved very much. It was conceived that the PEG-b-PLLA copolymer was mixed into the parent polymer, rather than being located in the interphase between PHB and PLLA.

Toughening of poly(3-hydroxybutyrate) with poly(cis-1,4-isoprene)

Abstract Poly(cis-1,4-isoprene) (PIP) was blended with poly(3-hydroxybutyrate) (PHB) to improve the mechanical properties of PHB. With the change in the blend composition there was virtually no shift in the Tg of either PIP or PHB, indicating that PHB and PIP were incompatible. Therefore, poly(vinyl acetate), which is compatible with PHB, was grafted onto PIP, and properties of the PHB/PIP-g-PVAc blend were characterized. As the concentration of the PIP-g-PVAc copolymer was increased in the PHB/PIP-g-PVAc blend, the Tg of the PHB rich domain was increased, while the Tg of the PIP rich domain remained nearly constant. It could be interpreted that the PVAc moiety of the graft copolymer was diffused into the PHB domain. The size of the dispersed phase of the PHB/PIP-g-PVAc blend was smaller than that of the PHB/PIP blend. The tensile properties and impact strength of the PHB/PIP-g-PVAc blends were superior to the PHB/PIP blends.

Properties of biodegradable copolyesters of succinic acid-1,4-butanediol/succinic acid-1,4-cyclohexanedimethanol

Although progress has been made in the study of biodegradable polyesters, little attention was given to aliphatic/alicyclic copolyesters. For this reason, we have undertaken systematic studies on the aliphatic/alicyclic copolyesters. As a first step in our research, we have presented the material characteristics (e.g., thermal and mechanical properties) and the biodegradability in different biological environments for a series of the aliphatic/alicyclic copolyesters that were synthesized by polycondensation of succinic acid, 1,4-butanediol, and 1,4-cyclohexanedimethanol. The chemical composition of the aliphatic/alicyclic copolyesters plays an important role in controlling the material characteristics and biodegradability. For the copolyesters with a mole fraction of succinic acid-1,4-cyclohexanedimethanol <0.3, an adjustment of the optimum between physical properties and biodegradability seems to be feasible.

Preparation and Characterization of Poly(Methyl Methacrylate) Coated TiO2 Nanoparticles

Titanium dioxide (TiO2) nanoparticles were modified with poly(methyl methacrylate) (PMMA) to improve the dispersion stability of the nanoparticles in a dielectric medium and to reduce the density mismatch between TiO2 and a dielectric medium for a microcapsule‐type electrophoretic display application. Nanoparticles were coated with PMMA by in situ dispersion polymerization. The PMMA‐coated TiO2 nanoparticles were characterized by fourier transform‐infrared spectrometrey (FT‐IR), electrophoretic light scattering (ELS), and scanning electron microscopy (SEM). Density of PMMA‐coated TiO2 nanoparticles was found to be dependent on the thickness of the PMMA coating on the nanoparticles. An increase of thermal stability of the PMMA layer and the contents of PMMA on the surface of the nanoparticles were measured via thermogravimetric analysis (TGA).

Strong interfacial attrition developed by oleate/layered double hydroxide nanoplatelets dispersed into poly(butylene succinate)

Poly(butylene succinate) (PBS) nanocomposite structure was studied as a function of the filler percentage loading. The resulting state of dispersion was evaluated by XRD and TEM, and the interfacial attrition between PBS chain and lamellar platelets by the melt rheological properties. Hybrid organic inorganic (O/I) layered double hydroxide (LDH) organo-modified by oleate anions was used as filler. It was found that the confinement supplied by the LDH framework forces the interleaved organic molecule to be more distant from each other than in the case of oleate salt, this having as an effect to decrease strongly the homonuclear intermolecular (1)H(1)H dipolar interaction. An additional consequence of this relatively free molecular rotation, affecting the (13)C CPMAS response as well, is to facilitate the delamination of the 2D-stacked layers during extrusion since an quasi-exfoliated PBS:Mg(2)Al/oleate structure is observed for filler loading lower than 5% w/w. This is in association to a non-linear viscoelasticity in the low-omega region and the observed shear-thinning tendency compares better than other PBS:silicate nanocomposite derivatives and is here explained by the presence of a percolated LDH nanoparticle network. Indeed the plastic deformation in the low-omega region is found to be restricted by well-dispersed LDH tactoids in association with a rather strong attrition phenomenon between tethered oleate anions and PBS chains.

Biodegradability of poly(3-hydroxybutyrate) blended with poly(ethylene-co-vinyl acetate) or poly(ethylene oxide)

Biodegradability of poly(3-hydroxybutyrate) (PHB) was determined by the modified Sturm test utilizing, activated sludge, or synthetic sludge and the result was more reproducible when the activated sludge was used as the microbial source. As PHB was blended with miscible poly(ethylene-co-85 wt% vinyl acetate) (EVA85), biodegradability of PHB was drastically reduced with the addition of EVA85. On the other hand, the biodegradation rate of the immiscible PHB/poly(ethylene-co-70 wt% vinyl acetate) (EVA70) blend was decreased gradually with an increase in the EVA70 content. Almost same biodegradation behavior was observed both for the PHB/EVA85 blend prepared by hot pressing of precipitation from chloroform solution into hexane and for the blend obtained by chloroform solvent casting. However, biodegradability of the PHB/poly(ethylene oxide) (PEO) blend was decreased rather slowly with an increase in the PEO content, even though it was a miscible blend.