Microwave-assisted green approach for graft copolymerization of l-lactic acid onto starch

ABSTRACT Poly l‐lactic acid grafted starch (St‐g‐PLA) copolymers were directly synthesized under microwave irradiation by using sodium hydroxide (NaOH) and stannous 2‐ethyl hexanoate acting as a catalyst, without the use of toxic solvents. The product were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (13C CP/MAS NMR), X‐ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA‐DTG). SEM analysis indicated that microwave heating had a considerable effect on the interfacial adhesion between PLA and starch. Thermogravimetric analysis (TGA‐DTG) revealed that copolymers exhibited better thermal stability. Maximum PLA grafting was achieved with the following reaction conditions: 450W microwave power, monomer ratio of 1:5 and 0.4M of NaOH. This study demonstrates that it is possible to obtain St‐g‐PLA copolymers with better processing characteristics and smaller sizes via microwave‐assisted synthesis. The applied procedure is an interesting “green” synthesis method for the production of biodegradable materials used in a diverse range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42937.