Synthesis of Well-Defined Graft Copolymers by Combination of Enzymatic Polycondensation and “Click” Chemistry

• Published in: Biomacromolecules 2010-12, Vol.11 (12), p.3660-3667
• Main Authors: Naolou, Toufik, Busse, Karsten, Kressler, Jörg
• Format: Article
• Language: English
• Subjects: Applied sciences; Azides; Exact sciences and technology; Fungal Proteins; Lipase - metabolism; Organic polymers; Physicochemistry of polymers; Polycondensation; Polyesters - chemical synthesis; Polyethylene Glycols; Polymers - chemical synthesis; Preparation, kinetics, thermodynamics, mechanism and catalysts; Surface Properties; Surface-Active Agents
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm1011085

Aliphatic polyesters having pendant azide groups were prepared by enzymatic polycondensation in the presence of lipase from Candida antarctica type B (CAL-B). The grafting reaction to the N3-functional polyester was carried out quantitatively at room temperature using copper-catalyzed azide−alkyne cycloaddition (CuAAC, “click” reaction) with monoalkyne-functional poly(ethylene oxide) (alkyne-PEO, M n = 750 g/mol). Furthermore, both enzymatic polycondensation and “click” reaction were carried out successfully in sequential one-pot reaction. The graft copolymer was surface-active and self-assembled in water. The graft copolymer had a critical aggregation concentration (cac) of 3 × 10−2 μM in water determined by surface tension measurements. Above cac, the graft copolymer formed single chains and aggregates having a hydrodynamic radius of ∼75 nm. Furthermore, the surface activity of the polymers at the air−water interface was studied by Langmuir trough measurements. The Langmuir isotherm of the graft polymer showed a pseudoplateau resulting from desorption of PEO chains into the subphase upon compression.