Glycerol copolyesters: control of branching and molecular weight using a lipase catalyst. Macromolecules 2005;38:3193–204

• Main Authors: Ankur S Kulshrestha, Wei Gao, Richard A Gross
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: antartic*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1085.1699; http://homepages.rpi.edu/%7Egrossr/_doc/publication/Macromolecules%202005%2038%203193%20ma0480190.pdf

ABSTRACT: Immobilized Lipase B from Candida antartica (Novozyme 435) catalyzed bulk polycondensations at 70°C for 42 h that resulted in hyperbranched polyesters with octanediol-adipate and glyceroladipate repeat units. Instead of using organic solvents, the monomers adipic acid (A2), 1,8-octanediol (B2), and glycerol (B′B2) were combined to form monophasic ternary mixtures. During the first 18 h of a copolymerization with monomer feed ratio (A2 to B2 to B′B2) 1.0:0.8:0.2 mol/mol, the regioselectivity of Novozyme 435 resulted in linear copolyesters. Extending the reaction to 42 h gave hyperbranched copolymers with dendritic glycerol units. The % regioselectivity for esterifications at the primary glycerol positions ranged from 77 to 82% and was independent of glycerol content in the monomer feed. Variation of glycerol in the monomer feed gave copolymers with degree of branching (DB) from 9 to 58%. In one example, a hyperbranched copolyester with 18 mol % glycerol-adipate units was formed in 90% yield, with M w 75 600 (by SEC-MALLS), Mw/Mn 3.1, and DB 19%. Generalized structures were created to depict that for hyperbranched glycerol copolyesters and the progression of products formed at reaction times from 5 min to 42 h.