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An innovative type of biodegradable thermoplastic elastomers with improved mechanical properties from very common and potentially renewable sources, poly(L-lactide)-b-poly(2-methyl-1,3-propylene glutarate)-b-poly(L-lactide) (PLA-b-PMPG-b-PLA)s, has been developed for the first time. PLA-b-PMPG-b-PLAs were synthesized by polycondensation of 2-methyl-1,3-propanediol and glutaric acid and successive ring-opening polymerization of L-lactide, where PMPG is an amorphous central block with low glass transition temperature and PLA is hard semicrystalline terminal blocks. The copolymers showed glass transition temperature at lower than −40 °C and melting temperature at 130–152 °C. The tensile tests of these copolymers were also performed to evaluate their mechanical properties. The degradation of the copolymers and PMPG by enzymes proteinase K and lipase PS were investigated. Microbial biodegradation in seawater was also performed at 27 °C. The triblock copolymers and PMPG homopolymer were found to show 9–15% biodegradation within 28 days, representing their relatively high biodegradability in seawater. The macromolecular structure of the triblock copolymers of PLA and PMPG can be controlled to tune their mechanical and biodegradation properties, demonstrating their potential use in various applications. [ABSTRACT FROM AUTHOR]

• 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]

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-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]