RESEARCH ARTICLE The effect of ethylene glycol on starch-g-PCL graft copolymer synthesis Aurelio Ramı ´rez-Hern andez 1 , Jos e L. Mata-Mata 1 , Alejandro Aparicio-Saguil an 2 , Gerardo Gonz alez-Garcı ´a 1 , H ector Hern andez-Mendoza 3 , Alfredo Guti errez-Fuentes 1 and Eduardo B aez-Garcı ´a 1 1 Exact Sciences Division, Department of Chemistry, University of Guanajuato, Guanajuato, M exico 2 Department of Food, University of Papaloapan, Tuxtepec, Oaxaca, M exico 3 Laboratorio Nacional de Investigaciones en Forense Nuclear (LANAFONU). Instituto Nacional de Investigaciones Nucleares (ININ), Carretera M exico-Toluca S/N 52750, La Marquesa Ocoyoacac, Estado de M exico, M exico The synthesis of the graft copolymer starch-g-PCL was carried out in a single phase, using molybdenum oxide as a catalyst, at a temperature of 150°C over a period of 24h. Infrared spectroscopy and nuclear magnetic resonance analyses indicated that the graft copolymer was successfully synthesized, obtaining an 84% conversion yield. The introduction of ethylene glycol to the reaction influences the copolymer synthesis, affecting conversion yields and the physicochemical properties of the resultant copolymer. X-ray diffraction analysis indicates that the copolymer crystallinity decreases as ethylene glycol concentration increases. An investigation of the thermal properties of the graft copolymer suggested that the decomposition temperature of the copolymer, compared to that of the homopolymer, decreases with exposure to ethylene glycol. Scanning electron microscopy revealed the formation of clusters between the starch granules and the grafted copolymer due to the interaction of the hydroxyl groups of the starch and PCL. Received: February 20, 2016 Revised: May 6, 2016 Accepted: May 7, 2016 Keywords: Graft copolymer / Ethylene glycol / Banana starch / PCL 1 Introduction Plastics can be found worldwide and are important for the development and growth of countries. Many of these plastics are non-biodegradable, and extensive use generates approxi- mately 25 million tons of waste per year. In 2014 alone, 308 million tons of plastic were consumed worldwide. This constitutes a major environmental problem with a variety of global impacts. Furthermore, the majority of these plastics are obtained from non-renewable, petroleum-based sources; during plastic synthesis, pollutants are directly discharged into the environment [1–5]. For these reasons, there is a great interest in producing biodegradable plastics based on natural polymers, such as starch. The chemical modification of starch that will allow it to generate layers with similar characteristics to conventional plastics, such as polyethylene (PE) and polypropylene (PP), is currently being investigated. Starch itself generates layers but with different physical and chemical properties from petroleum-based polymers [6–10]. Polylactones, such as poly(e-caprolactone) (PCL), have been used to chemically modify starch and form a highly biodegradable starch-g-PCL graft copolymer. This copolymer has a wide range of possible applications in the plastics, pharmaceutical and food industries [11, 12] and can be considered an alternative to conventional plastics. For starch-g-PCL copolymer synthesis, a wide variety of catalysts have been used, including N-methylimidazole (NMI), aluminum triisopropoxide [Al(OiPr) 3 ], and tin(II) 2-ethylhexanoate [Sn(Oct) 2 ]. There are many acceptable starch sources, such as corn and potatoes, and the conversion yields obtained can reach 52% [13–19]. This conversion yield Correspondence: Prof. Ramírez-Hern andez Aurelio, Exact Sciences Division, Department of Chemistry, University of Guanajuato, Noria Alta S/N, C.P. 36050, Guanajuato, M exico E-mail: chino_raha@hotmail.com Abbreviations: EG, ethylene glycol; PCL, poly(e caprolactone); S1, sample 1; S2, sample 2; S3, sample 3; S4, sample 4; S5, sample 5; DSPCL, degree of substitution of the PCL graft on starch DOI 10.1002/star.201600070 1148 Starch/Stärke 2016, 68, 1148–1157 www.starch-journal.com ß 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim