Topology Characterization by MALDI-ToF-MS of Enzymatically Synthesized Poly(lactide-co-glycolide)

Abstract

Lipase catalyzed copolymerization of the monomers lactide and glycolide by Pseudomonas cepacia employing a molar ratio of 80L/20G has been studied. The copolymers were characterized by MALDI-ToF-MS, DSC, SEC and NMR. MALDI-ToF-MS has successfully been used not only to determine end groups and chemical composition but even the microstructure of the copolymers. We demonstrated that for this lipase catalyzed copolymerization, the main product of the reaction at 100 degrees C was linear homopolymer of lactide while at 130 degrees C the main product was cyclic random copolymer.

Enzymatic synthesis of poly-l-lactide and poly-l-lactide-co-glycolide in an ionic liquid

“…They obtained average molecular weights (M w ) up to 20.6 9 10 3 g/mol, but polymer yields were not reported. Also in that work, significant copolymerizations without enzyme were detected, attributing them to a cationic mechanism induced by traces of hydroxyacid from the monomer when synthesis was carried out at relatively high temperatures [11].…”

“…However, in bulk experiments, PLLA is also obtained even in the absence of biocatalyst [8]. Previous reports on the synthesis of PLLGA are restricted to the work of Huijser et al who used lipase PS in bulk at relatively high temperatures (100-130°C), and paid particular attention to elucidating PLGA structures and topology from MALDIToF-MS data, using an ''in-house developed software'' [11]. They obtained average molecular weights (M w ) up to 20.6 9 10 3 g/mol, but polymer yields were not reported.…”

Hydrolases Part I: Enzyme Mechanism, Selectivity and Control in the Synthesis of Well-Defined Polymers

“…It is conceivable that another non-enzymatic mechanism contributed in these polymerizations. In fact, Koning and coworkers synthesized copolymers of glycolide and lactide using immobilized P. cepacia lipase and pointed out the possibility of a cationic mechanism being operational during the enzymatic polymerization [138].…”

Chiral Polymers by Lipase Catalysis

“…This difference in reactivity has been attributed to the Rconfi guration of the secondary alcohol obtained after ring opening of the d -lactide, whereas a non -propagating alcohol of the S -confi guration is formed for l -lactide. Later on, the copolymerization of l -lactide with glycolide using both free and immobilized Burkholderia cepacia lipase ( BCL ) was investigated [21] . At reaction temperature of 100 -130 ° C, copolymers with small amounts of glycolyl repeat units were formed according to careful MALDI -TOF -MS analysis.…”