Candida antartica lipase B catalyzed polycaprolactone synthesis: Eects of organic media and temperature

• Main Authors: Ajay Kumar, Richard A Gross
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2000
• Subjects: Antarc*; Antarctica; antartic*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1085.48; http://homepages.rpi.edu/%7Egrossr/_doc/publication/Biomacromolecules%202000%201%20133%20bm990510p.pdf

Engineering of the reaction medium and study of an expanded range of reaction temperatures were carried out in an effort to positively influence the outcome of Novozyme-435 (immobilized Lipase B from Candida antarctica) catalyzed -CL polymerizations. A series of solvents including acetonitrile, dioxane, tetrahydrofuran, chloroform, butyl ether, isopropyl ether, isooctane, and toluene (log P from -1.1 to 4.5) were evaluated at 70 C. Statistically (ANOVA), two significant regions were observed. Solvents having log P values from -1.1 to 0.49 showed low propagation rates (e30% -CL conversion in 4 h) and gave products of short chain length (M n e 5200 g/mol). In contrast, solvents with log P values from 1.9 to 4.5 showed enhanced propagation rates and afforded polymers of higher molecular weight (M n ) 11500-17000 g/mol). Toluene, a preferred solvent for this work, was studied at -CL to toluene (wt/vol) ratios from 1:1 to 10:1. The ratio 1:2 was selected since, for polymerizations at 70°C, 0.3 mL of -CL and 4 h, gave high monomer conversions and M n values (∼85% and ∼17 000 g/mol, respectively). Increasing the scale of the reaction from 0.3 to 10 mL of CL resulted in a similar isolated product yield, but the M n increased from 17 200 to 44 800 g/mol. Toluene appeared to help stabilize Novozyme-435 so that lipase-catalyzed polymerizations could be conducted effectively at 90°C. For example, within only 2 h at 90 C (toluene-d 8 to -CL, 5:1, ∼1% protein), the % monomer conversion reached ∼90%. Also, the controlled character of these polymerizations as a function of reaction temperature was evaluated.