Synthesis of copoly(d,l-lactic acid) with relatively low molecular weight and in vitro degradation

✍ Scribed by Hironobu Fukuzaki; Masaru Yoshida; Masaharu Asano; Minoru Kumakura

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 642 KB
• Volume: 25
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(89)90131-6

✦ Synopsis

Copoly(o-lactic acid/L-lactic acid; o-LA/L-LA) with relatively low molecular weight (/14nll of 300-3800, was synthesized by direct copolycondensation without catalyst in an atmosphere of nitrogen at 200 C, to evaluate the difference in degradation between crystalline and amorphous copolymers. The non-enzymatic degradation of crystalline copolymer, e.g. a copoly(o-LA/L-LA, 2/98 mol%), showed a parabolic-type degradation pattern in the h3. 900 to 2700 range; degradation preferentially occurs in the amorphous regions because the matrix remains highly crystalline in the initial stages. In contrast, the non-enzymatic degradation of amorphous copolymer, e.g. a copoly(o-LA/L-LA, 50/50 mol%), can be divided into three types according to ~St n, viz. parabolic-type for /Qn = 1500, linear-type for :Qn = 2200, S-type for M~ = 3500. For comparison, the copolymers were degraded in the presence of enzymes; the process was markedly accelerated by the action of esterase-type enzymes, of which Rhizopus delemer lipase gave the highest degradation activity.