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In order to utilize biodegradable polymers as a functional material, it is important to make the best use of their biodegradability. Biodegradation of aliphatic polyesters, such as PCL, PBSA and P3HB, in seawater was investigated. BOD test using seawater and field test were carried out. As for BOD test, several factors were investigated such as tide, preservation of seawater, sampling place, population of microorganism, and seawater temperature. Biosynthesized P3HB and PHBHH showed rapid biodegradation by BOD method. As for synthetic polyesters, PCL also degraded fast. However, PBSA which is a popular biodegradable polymer in soil was not always biodegraded by BOD method with seawater. PBS and PBAT showed much slow biodegradation. Solvent cast films were immersed in the sea at a depth of 1.5 m. After 4 weeks, the weight loss of P3HB film was about 90%. On the contrary, the biodegradation by BOD method for 4 weeks was around 50%. Synthetic polyesters also showed obvious weight loss in field test, in contrast to the BOD results. • Marine biodegradation of various polyesters were examined by BOD method and Field test. • Some synthetic polymers did not show obvious biodegradation by BOD test in spite that they were biodegraded well in the sea. • BOD test is a useful method to examine factors effected on biodegradation. [ABSTRACT FROM AUTHOR]

Abstract: Copolyesteramides of 2-pyrrolidone with ε-caprolactone were synthesized by ring-opening copolymerization. The copolymers were random-like and their melting temperature and heat of fusion were dependent on the polymer composition. Biodegradation by a polyamide 4 (PA4) degrading microorganism showed rapid degradation in the region of amide-rich polymer composition. On the contrary, enzymatic hydrolysis using a lipase resulted in a different tendency, that is, ester-rich copolymers hydrolyzed rapidly. Activated sludge makes copolymers degrade to CO2 in wide polymer composition ratio. Copolyesteramides are expected to be applied as an environmentally-friendly plastics or bioabsorbable polymers in medical fields. [Copyright &y& Elsevier]

Abstract: Copolyesters of poly(ε-caprolactone) diol and 1,18-octadecane dicarboxylic acid were synthesized by polyaddition. The copolymers have a "mixed" structure of ’polyester-polyethylene’. Characterization was carried out by using 1H and 13C NMR, FT-IR, viscosities, DSC, and GPC. The tensile strength varied from 11.9 to 19.9 MPa, and elongation at break varied from 370 to 660 %, respectively. Biodegradability was evaluated by enzymatic hydrolysis (lipases from Rhizopus arrhizus and Candida cylindracea and an esterase form hog liver) and by soil burial test. Both tests showed that the copolyesters were characterized by enhanced biodegradability. [Copyright &y& Elsevier]

• The aliphatic polyesters from 2-methyl-1,3-propanediol (MP) and dicarboxylic acids bearing 7–10 carbons were prepared, demonstrating their high biodegradability in seawater. • Poly(2-methyl-1,3-propanediyl azelate) (PMP9) showed the lowest glass transition temperature among them. • The ring-opening polymerization (ROP) of L-lactide using PMP9 as a macroinitiator gave PLLA- b -PMP9- b -PLLA (TPE9), which exhibit excellent physical properties as thermoplastic elastomers. • One-pot synthesis of a TPE9 was achieved by the successive polycondensation MP and azelaic acid followed by the ROP of L-lactide. • The TPE9s were also biodegraded in seawater. Elastic materials with high biodegradability should replace those with low biodegradability in some applications. We previously reported biodegradable thermoplastic elastomers (TPEs) composed of poly(l -lactide) (PLLA) as a hard segment and aliphatic polyesters from 2-methyl-1,3-propanediol (MP) and short aliphatic dicarboxylic acids as soft segments. In this study, we synthesized the biodegradable thermoplastic elastomers using longer aliphatic dicarboxylic acids to develop the TPEs with lower glass-transition temperature (T g) and high biodegradability. A series of aliphatic polyesters were prepared by polycondensation of MP and aliphatic dicarboxylic acids bearing 7–10 carbons. Among them, poly(2-methyl-1,3-propylene azelate) (PMP9) was found to have lower T g , amorphous nature, and high biodegradability in seawater. The ring-opening polymerization of l -lactide (LLA) using PMP9 as a macroinitiator afforded triblock copolymers, PLLA- b -PMP9- b -PLLA (TPE9). The successive addition of LLA to in-situ generated PMP9 resulted in the successful one-pot synthesis of high molecular weight TPE9. The TPE9s showed both low T g of the PMP9 segment and high melting temperature of the PLLA segment. The TPE9s exhibited elastic behavior showing elongation at break of up to 2500 % in tensile tests and also high biodegradability in seawater. Thus, we developed potentially practical TPE with tunable physical properties and high biodegradability obtainable from easily available and renewable starting materials. [ABSTRACT FROM AUTHOR]

A biodegradable polymer–titanium dioxide (TiO 2) nanocomposite with antimicrobial activity by photooxidation of the composited TiO 2 under fluorescent light irradiation was investigated. Polyamide 4 (PA4)–visible-light-sensitive TiO 2 nanocomposite films were prepared. The nanocomposite films exhibited antibacterial activity slightly in the dark, whereas antibacterial activity against Escherichia coli was enhanced according to the increase of TiO 2 concentration under fluorescent light irradiation for 1 h at 4000 lx. As the increase of the illumination intensity and irradiation time, nanocomposite films exhibited high antibacterial activity. The cell count on nanocomposite films with 1 wt% TiO 2 decreased three orders of magnitude comparing to that of films without TiO 2 under irradiation for 6 h at 3000 lx. Staphylococcus aureus was resistant to PA4-TiO 2 nanocomposites in contrast to E. coli. In contrast, a PA4-degrading bacteria (ND-11) was sensitive to PA4-TiO 2 nanocomposites comparing E. coli. In addition, the PA4-degrading bacteria was sensitive to the copper containing in TiO 2. Therefore, the biodegradability was reduced according to the increase the TiO 2 (copper) concentration in PA4-TiO 2 nanocomposites in the dark. It was suggested that the effects of TiO 2 against microbial differ from every biodegradable polymer. In this study, we were able to impart a biodegradation control function, in which biodegradation is suppressed by fluorescent light irradiation and progressed in the dark, to PA4 by compositing visible-light-sensitive TiO 2. • Biodegradable polymer–TiO 2 nanocomposite with antimicrobial activity upon fluorescent light irradiation was investigated. • We described a method of controlling biodegradation of PA4 by generating a composite with visible-light-sensitive TiO 2. • Biodegradation is suppressed by exposure to light, and activated in the dark. [ABSTRACT FROM AUTHOR]

Herein, we report on the aquatic degradation of polyamide (nylon) 4. Polyamide 4 (PA4) has previously been shown to degrade in natural environments such as activated sludge and soil, as well as in vivo (when subcutaneously implanted in the backs of rats). In laboratory biodegradation tests of PA4, polyhydroxybutyrate (PHB), and polycaprolactone (PCL) in sampled seawater, the amount of oxygen absorption increased over time. PA4 degraded by about 30% in 4 weeks, which is comparable to that of PCL (30%) but less than that of PHB (60%). PA4 films were immersed in the sea and recovered at adequate intervals and weighed. The weight of the films decreased by 10–70% in 6 weeks, showing that PA4 is degraded in actual aquatic (sea) environments. We isolated PA4-degrading bacteria, strain MND-1, from the seawater used in the laboratory degradation tests. MND-1 is thought to belong to the family Alteromonadaceae from the DNA sequence of 16S rDNA. Gamma-aminobutyric acid (GABA) and GABA oligomers were detected in the PA4 degradation products. This indicates that the strain MND-1 hydrolyzes the amide bonds of PA4 into GABA oligomers and GABA. • We investigated the degradability of PA4 in seawater and in the sea. • PA4 was degraded in various seawaters in laboratory tests. • The weight of PA4 samples decreased in field degradation tests. Hence it was clarified that PA4 is degraded in the sea. • PA4-degrading bacteria MND-1 was purified and identified from seawater. • PResults of the degradation products analysis suggested that the isolated degrading bacteria degrades PA4 by hydrolysis. [ABSTRACT FROM AUTHOR]

We determined that polyamide 4 (PA4), which is easily degraded in the environment, is also degraded in vivo . We previously reported that PA4 was degraded by activated sludge. However, the potential biodegradability of PA4 in vivo has not been evaluated. In the present study, we subcutaneously implanted various PA4 samples in the backs of rats, including non-woven fabric as well as film and mold. The weights of implanted and recovered non-woven cloth composed of the PA4 polymer started to decrease at 3 months. At 8.5 months, weights decreased by 90%. For the non-woven PA4 cloth with a fine structure, there was no significant decrease in weight until 8.5 months. These results showed that PA4 was degraded in vivo and that polymer structure was important in determining the degradation rates. Copolymers composed of PA4 and polycaprolactone were also degraded in vivo . Homopolymers of PA4 were not hydrolyzed in phosphate buffer at 37 °C after one year. These results suggested the possibility that biochemical reactions were implicated in the degradation of PA4 in vivo . Based on tissue sample observations, implanted PA4 did not modify surrounding tissues. Safety evaluation, mutagenicity testing using bacteria (Ames test), and in vitro cytotoxicity testing using Chinese hamster V79 cells suggested that PA4 had no mutagenicity or cytotoxicity. Our study demonstrates that PA4 has potential as a bioabsorbable polymer material for biomedical applications. [ABSTRACT FROM AUTHOR]

Polyamide 4 (PA4) is a biodegradable polymer that can be produced from biomass. We found that modifying the terminal group of PA4 with a long-chain fatty acid resulted in the suppression of its biodegradation. PA4 modified with various acyl compounds from acetyl (C2) to stearoyl (C18) chlorides were prepared and used for biodegradation tests. The biodegradation of the PA4s was evaluated using PA-4-degrading bacteria ( Pseudomonas sp. ND-11) and activated sludge. The PA4-degrading bacteria grew and formed a clear zone around the colonies on the media containing PA4s with C2, C3, C6, and C10 end groups. On the other hand, PA4s with C12, C14, C16, and C18 end groups were not significantly degraded. Similar results were obtained using activated sludge. These results showed that the biodegradability of PA4 could be controlled by the molecular design of the polymer end group. Blending PA4 with fatty acid-functionalized PA4 decreased its biodegradability depending on the blend ratio. From the results of the contact angle measurements on the PA4 surfaces, it was suggested that the biodegradability was correlated to the hydrophilicity of the polymers. This method of controlling the biodegradability by adding a fatty acid group could be applied to other biodegradable polymers such as poly(butylene succinate adipate)s, ε-poly(caprolactone), and poly(lactic acid). [ABSTRACT FROM AUTHOR]

Poly-(l)-lactic acid (PLLA) was solvolyzed with polyethylene glycol (PEG) with different ratios of PLLA and PEG under dry conditions. The obtained materials were found to be the block copolymer of PLLA and PEG (PLLA/PEG) from NMR analysis of which the number average molecular weights ranged from 6 × 103 to 2 × 104 g mol−1. The films of stereocomplex (SC) of PLLA/PEG and poly-(d)-lactic acid (PDLA) were prepared by solvent casting method, and the thermal properties and the contact angle of the films were examined. The melting temperatures of PLLA/PEG and the corresponding SC with PDLA linearly decreased with the increase in the PEG content from 110 to 170 °C. The contact angle of PLLA/PEG became lower when the PEG content in the PLLA/PEG was higher, while their SCs with PDLA showed no clear correlation with the PEG content. Biodegradability of PLLA/PEGs and their SCs were also investigated with respect to the EG content. [ABSTRACT FROM AUTHOR]

• Poly(L-lactide)- b -poly(2-methyl-1,3-propanediyl adipate)- b -poly(L-Lactide) (PLLA- b -PMPS- b -PLLAs) were synthesized as new biodegradable thermoplastic elastomers. • The triblock copolymers showed T g at lower than −40 °C and T m at around 150 °C. • Their tensile tests demonstrated their low modulus and high elongation. • The triblock copolymers and PMPA were found to be highly biodegradable in seawater. As a promising biodegradable and biorenewable alternative to ubiquitous petrochemical plastics, poly(L-lactide) (PLLA) can be widely employed in biomedical and pharmaceutical fields. In this work, triblock copolymers, poly(L-lactide)- b -poly(2-methyl-1,3-propanediyl adipate)- b -poly(L-lactide) (PLLA- b -PMPA- b -PLLA)s, were synthesized by two-step polymerization from 2-methyl-1,3-propanediol (MP), adipic acid (AA) and L-lactide (LLA) as new biodegradable thermoplastic elastomers. The copolymers exhibited glass-transition temperature at below −40 °C and melting temperature at 140–160 °C. These copolymers showed much higher elongation at break and lower tensile modulus than those of PLLA. Enzymatic degradation tests of the obtained copolymers were performed using proteinase K and lipase PS as catalysts in hydrolysis reaction to demonstrate rapid degradation for these copolymers. Seawater biodegradability test was conducted for 28 days for each sample. The triblock copolymer and PMPA homopolymer were found to show about 50% biodegradation within 28 days representing very high biodegradable property in seawater. [ABSTRACT FROM AUTHOR]

• Poly(2-methyl-1,3-propanediyl succinate) (PMPS) was applied as a soft segment. • PLLA- b -PMPS- b -PLLAs were synthesized as new biodegradable thermoplastic elastomers. • The triblock copolymers showed T g at lower than −20 °C and T m at around 150 °C. • Their tensile tests demonstrated their low modulus and high elongation. • Their biodegradation tests were performed using enzymes and seawater. Triblock copolymers, poly(L-lactide)- b -poly(2-methyl-1,3-propanediyl succinate)- b -poly(L-lactide) (PLLA- b -PMPS- b -PLLA), were synthesized as new biodegradable thermoplastic elastomers by two-step polymerization. In the first step, hydroxy-telechelic poly(2-methyl-1,3-propanediyl succinate) (PMPS) was synthesized from 2-methyl-1,3-propanediol (MP, small excess) and succinic acid (SA) using two-stage reaction of esterification and simple polycondensation processes. In the second step, plant derived L-lactide (LLA) was polymerized using the bifunctional PMPS as a macroinitiator to synthesize PLLA- b -PMPS- b -PLLA triblock copolymers. The structures of the triblock copolymers as well as the PMPS macroinitiator were characterized by NMR and GPC analysis. PMPS is an amorphous polymer with T g at lower than −24 °C. The triblock copolymers also exhibited low T g for the PMPS segment at lower than −20 °C as well as T m at around 150 °C for the PLLA segment. The tensile tests of the triblock copolymers demonstrated their low modulus and high elongation. The biodegradation tests of these polymers were also performed using enzymes and seawater to reveal their biodegradability. [ABSTRACT FROM AUTHOR]

Aromatic polyesters such as poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT) and poly(butylene terephthalate) (PBT) are widely used all over the world due to their excellent physical properties. However, their degradation in the environment is very slow and the environmental load of their wastes is a potential problem. On the other hand, poly(l -lactic acid) (PLLA) and poly(glycolic acid) (PGA) have attracted attention for their biodegradability. We expected that periodic copolyesters composed of hydroxy acids, ethylene glycol, and terephthalic acid can be biodegradable polymer with relatively high melting points. In this study, a series of novel periodic copolyesters was synthesized and their physical properties and biodegradabilities were investigated. The 2:1 condensation products (LEL and GEG) of l -lactic acid (LA) or glycolic acid (GA) and ethylene glycol were synthesized from the reaction of potassium salt of LA or GA with 1,2-dibromoethane. Then, the polycondensation of LEL or GEG with chloride derivatives of dicarboxylic acids (terephthalic acid, 2,5-furandicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and adipic acid) were performed to produce a series of periodic copolyesters such as poly((ethylene diglycolate) terephthalate) (poly(GEGT)) and poly((ethylene di(l -lactate)) terephthalate) (poly(LELT)). The most of the copolyesters with LA units such as poly(LELT) were amorphous. In contrast, the copolyesters with GA units exhibited relatively high melting temperature (e.g. T m = 209 °C for poly(GEGT)). The preliminary degradation tests of poly(GEGT) and poly(LELT) were performed. The obtained poly(GEGT) showed biodegradability in seawater at 27 °C. A series of novel periodic copolyesters was synthesized and their physical properties and biodegradabilities were investigated. The 2:1 condensation products of l -lactic acid or glycolic acid and ethylene glycol were synthesized from the reaction of potassium salt of those hydroxy acids with 1,2-dibromoethane. Their polycondensation with chloride derivatives of dicarboxylic acids (terephthalic acid, 2,5-furandicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and adipic acid) produced a series of periodic copolyesters such as poly((ethylene diglycolate) terephthalate) (poly(GEGT)) and poly((ethylene di(l -lactate)) terephthalate) (poly(LELT)). The copolyesters with glycolate units exhibited relatively high melting temperature (e.g. T m = 209 °C for poly(GEGT)). The preliminary degradation tests of poly(GEGT) and poly(LELT) revealed the biodegradability of the poly(GEGT) in seawater. Image 1 • New periodic copolyesters composed of ethylene glycol, terephthalic acid, and glycolic acid or l -lactic acid were synthesized. • Poly((ethylene diglycolate) terephthalate) (poly(GEGT)) showed relatively high T m at 209 °C. • Poly(GEGT) exhibited biodegradability in seawater at 27 °C. • Both copolyesters were hydrolyzed at 70 °C. [ABSTRACT FROM AUTHOR]