Lipase-Catalyzed Synthesis and Characterization of Biodegradable Polyester Containing L-Malic Acid Unit in Solvent System

Lipase-catalyzed direct polycondensation of L-malic acid (L-MA), adipic acid, and 1,8-octanediol in organic media was achieved using Novozym 435 as the biocatalyst. H-1-nuclear magnetic resonance spectroscopy indicated that the selectivity of Novozym 435 was unaffected by changes in the organic media. The molecular weight (M-w) of the copolymers was affected by the L-MA feed ratio in the diacids, hydrophobicity of the solvent, and solubility of the substrates in the solvents. The M-w reached a maximum of 17.4 kDa at 80 degrees C in isooctane at L-MA feed ratio in the diacids of 40 mol %. The M-w increased from 3.2 to 16.6 kDa when the reaction time was extended from 6 to 48 hr at 70 degrees C, and remained relatively constant with further increases in reaction time from 48 to 72 hr. The hydrophilicity, thermal stability, and crystallizability of the copolymer were also investigated. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1114-1120, 2011