Aliphatic polyesters biodegradable

As far as biodegradable aliphatic polyesters are concerned, a main classification divides them into two groups. In the first group, the repetitive unit of the polymer is constituted by a hydroxyacid unit, while in the second one it is constituted by a diol 

They can be obtained both by microbial or synthetic methods, the latter being the most common and are generally known to be susceptible to biological attack [2-6]. 

The synthesis and properties of these polyesters have been studied since 1930s by Carothers and co-workers [7, 8], but it is only from the 1970s that their biodegradability has been investigated [2, 9]. 

The various factors which can affect the degradation of aliphatic polyesters are now considered. For the sake of clarity, each type will be discussed separately. 

Degradation of LA/GA polymers is rather complex. It depends not only on experimental parameters such as pH, ionic strength, temperature and implantation site, but also on polymer characteristics such as MW, MW distribution, morphology, additives, size, chemical composition and configurational structures [16, 61,95]. 

Polymer morphology, (i.e. semicrystallinity and chain orientation) plays a critical role in degradation phenomena. It is now well known that degradation of 

Ginde and Gupta examined the influence of polymer morphology on the chemical degradation of PGA fibres and pellets [53]. The degradation rate was 

Zhu et al carried out an in vivo degradation study of several dl-LA/G A homo-and copolymers and found that all corresponding threads were completely absorbed by 60 days [115]. Ogawa et al, studied in vivo degradation of 1 x 10 x 10 mm plates made of dl-LA/G A polymers and found that both the lag time and the half-life decreased with the increase in GA content [116]. Amarpreet and Hubbell prepared a series of 66 terpolymers of DL-lactide, glycolide and e-caprolactone [117]. The half-lives of these polymers were found to vary from a few weeks to several months. 

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What Is a biodegradable polymer Give an example of a biodegradable aliphatic polyester. 

Coulembier O, Degee Ph, Hedrick JL, Dubois Ph (2006) From controlled ring-opening polymerization to biodegradable aliphatic polyester especially poly(P-malic acid) derivatives. Prog Polym Sci 31 723-747... 

Yoshikawa Y, Ofuji N, Imaizumi M, Moteki Y, Fujimaki T (1996) Molecular weight distribution and branched structure of biodegradable aliphatic polyesters determined by s.e.c-MALLS. Polymer 37 1281... 

BMM623>, /3-valerolactone <2002JA15239>, and a-methyl-/3-pentylpropiolactone <2004T7177>. The polyester formed from the latter monomer was used in the formulation of immiscible blends or block copolymers with the biodegradable aliphatic polyester polylactide <2004T7177>. 

Beside the natural polyesters a number of synthetic aliphatic polyesters have also been shown to be biodegradable. From a commercial point of view the most important synthetic biodegradable aliphatic polyester was traditionally polycaprolactone (PCL). 

Title Biodegradable Aliphatic Polyester Grafted with Poly(Ethylene Glycol) Having Reactive Groups and Preparation Method Thereof... 

Title Simplified Method of Producing Biodegradable Aliphatic Polyesters... 

Nonetheless, artificial biodegradable aliphatic polyesters are still mainly based on the industrial polymerization of monomers such as glycolic acid (PGA), lactic acid (PLA), and caprolactone (PCL). (See Figure 12.29). These polyesters are applied in implants, absorbable sutures, controlled-release packaging, and degradable films and moldings. 

Biodegradable, aliphatic polyesters can be synthesized or produced by bacteria and cyanobacteria. These organisms accumulate poly(3-hydroxy butyrate) (PHB) up to 80 wt% of the dry cellular material. Long branching has been produced by modifying the culture medium [Ramsay et ah, 1991]. PHB is degraded by the enzyme poly(3-hydroxybutyrate depolymerase). 

Typical diol-diacid type biodegradable aliphatic polyesters, PBA and PBS, were degraded in a diluted toluene solution by the immobilized lipase CA which exclusively formed the cyclic oligomers. Their composition was partially dependent on the degradation conditions, such as the enzyme concentration and temperature. On the other hand, in a more concentrated condition, the cyclic oligomer was readily repolymerized by the ring-opening polymerization. 

Poly(butylene succinate) (PBS) is an important member of biodegradable aliphatic polyester family. PBS and related copolymers have shown considerable promise for uses as environmentally biodegradable thermoplastics, as well as bioabsorbable/biocompatible medical materials (/). In both cases, practical applications require that the polymer possess a high molecular weight (M >20,000) so that it can have useful mechanical properties. 

ASTM American Society for Testing Materi- BDP biodegradable (aliphatic) polyester... 

Drug delivery systems based on biodegradable aliphatic polyesters have advanced remarkably over the past few decades. Commonly used polymers such as poly(e-caprolactone) (PCL), poly (lactide acid) (PLA), and poly (lactic-co-glycolic acid) (PLGA) are FDA approved and well known for their biodegradability, biocompatibility, and non-toxic properties, which make them suitable as matrices for controlled release drug delivery systems. 

Kricheldorf, H. R., Langanke, D., Spickermann, J., and Schmidt, M., Macrocydes. 10. Macrocyclic Poly(l,4-butanediol-esters)s by Polycondensation of 2-Stanna-1,3-dioxepane with Dicarboxylic Acid Chlorides, Macromolecules, 32,3559,1999. Jedlinshi, Z., Juzwa, M., Adamus, G., Kowalczuk, M., and Montaudo, M., Anionic Polymerization of Pentadecanolide. A New Route to a Potentially Biodegradable Aliphatic Polyester, Macromol. Chem. Phys., 197, 2923,1996. 

Table 8.1 Physical properties of some biodegradable aliphatic polyesters [8]. (Reproduced with permission from ref [8] 2002, Wiley-VCH Verlag Gmbhi Co. KGaA.)... 

Tserki, V, Matzinos, R, PavUdou, E. et al. (2006) Biodegradable aliphatic polyesters. Part 1. Properties and biodegradation of poly (butylene succinate-co-butylene adipate). Polymer Degradation and Stability,... 

In addition to PLA or PCL, the synthesis of other biodegradable aliphatic polyesters via ROP of monomers such as rac-p-butyrolactone (rac-BBL) could be catalysed by titanium precursors, though up till now this has been somewhat under investigated (Scheme 6.11). ... 

PBS is one of the members of the family of biodegradable aliphatic polyesters. A number of copolymerization attanpts have been made to improve its properties (Darwin et al. 2003 Jin et al. 2000b, c, d, 2001). For example, Jin et al. (2000b, c) introduced phenyl units into the side chain of PBS, leading to better biodegradability of the copolyesters. Jung et al. (1999) successfully synthesized new PBS copolyesters containing alicyclic 1,4-cyclohexanedimethanol. 

Taniguchi I, Nakano S, Nakamura T, El-Salmawy A, Miyamoto M, Kimura Y (2002) Mechanism of enzymatic hydrolysis of poly(butylene succinate) and poly(butylene succinate-co-L-lactate) with a lipase from Pseudomonas cepacia. Macromol Biosci 2 447-455 Tomita K, Kuroki Y, Hayashi N, Komukai Y (2000) Isolation of a thermophile degrading poly(butylene succinate-co-butylene adipate). J Biosci Bioeng 90 350-352 Tserki V, Matzinos P, PavUdou E, Panayiotou C (2(X)6a) Biodegradable aliphatic polyesters. Part II. Synthesis and characterization of chain extended poly(butylene succinate-co-butylene adipate). Polym Degrad Stab 91 377-384... 

Y. Fujita and O. Sawa, Ester compound, plasticizer for biodegradable aliphatic polyester resin, and biodegradable resin composition, US Patent 7166654, assigned to Daihachi Chemical Industry Co., Ltd. (Osaka, JP), January 23, 2007. 

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