Polysaccharide Nanocomposites Reinforced with Graphene Oxide and Keratin-grafted Graphene Oxide
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Polysaccharide Nanocomposites Reinforced with Graphene Oxide and Keratin-grafted Graphene Oxide Claramaría González1,2, Ana Hernández2,3, Víctor Castaño2, Oxana Kharissova1, Rodney Ruoff 4 and Carlos Velasco-Santos2,3 1 Universidad Autónoma de Nuevo León, Monterrey, México. 2Centro de Física Aplicada y Tecnología Avanzada, UNAM, Querétaro, México. 3Instituto Tecnológico de Querétaro, Querétaro, México. 4The University of Texas at Austin, USA. ABSTRACT Nanocomposites of polysaccharide matrices, chitosan-starch and carboxymethyl cellulose-starch reinforced with graphene oxide and graphene grafted with keratin were developed. Composites films had been prepared for the casting/solvent evaporation method. The nanocomposites of chitosan/starch matrix improved substantially their mechanical properties with respect to the film without reinforcing, obtaining an increase of 929 % in the storage modulus (E’ 35ºC) with only 0.5 wt% of graphene oxide and outstanding increments in E’ at 150ºC and 200ºC when keratin grafted graphene oxide is incorporated (0.1 wt%). In contrast, the graphene oxide incorporated into the carboxymethyl cellulose-starch matrix tends to decrease the stiffness of the film behaving in opposite way to nanocomposite of chitosan/starch matrix. INTRODUCTION During the last two decades significant efforts have been made towards to diminish the impact of man to the environment. Following this tendency, it has tried to replace polymers derived from petroleum by those biodegradable ones. In this sense, the biopolymers glimpse like a possible alternative to this attempt, nevertheless, is necessary to improve some of their properties to position them like competitive materials front to the fossil derivatives. The technology of nanocomposites is an elegant answer to this problematic. The nanocomposites consist of a polymeric matrix or continuous phase and a discontinuous phase or filler where this one has at least one dimension smaller than 100 nm [1]. Different nanomaterials have been used as reinforcement of polymer matrices; however, the discovery of the graphene, a single layer of carbon atoms covalently bonded in a hexagonal crystalline structure, has attracted enormous interest by the exceptional properties that present [2-4]. The graphene oxide, its oxygenated counterpart, presents numerous groups oxygenated -hydroxyl, epoxy and carboxyl- in the basal planes and the borders of the sheet that serve like sites of chemical anchorage [5]. These groups could to allow improving the distribution of the graphene oxide sheets and to generate interfacial bonding with the hanging groups of natural polymers matrices. Recently, the graphene oxide sheets have been modified with various organic molecules providing them of interesting new properties [6-8]. Based on this background, we use keratin obtained from chicken feather to change the behavior of graphene oxide sheets. Keratin, a fibrous protein, is durable, insoluble and present mechanical properties of strength and flexibility [9]. These properties and the large numbe
