Glycerol copolyesters: Control of branching and molecular weight using a lipase catalyst

Immobilized Lipase B from Candida, antartica (Novozyme 435) catalyzed bulk polycondensations at 70 degrees C for 42 h that resulted in hyperbranched polyesters with octanediol-adipate and glycerol-adipate repeat units. Instead of using organic solvents, the monomers adipic acid (A(2)) 1,8-octanediol (132), and glycerol (B'B-2) were combined to form monophasic ternary mixtures. During the first 18 h of a copolymerization with monomer feed ratio (A(2) to B-2 to B'B-2) 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, 75 600 (by SEC-MALLS), M-w/M-n 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.