Materials Today Communications 25 (2020) 101633 Available online 9 September 2020 2352-4928/© 2020 Elsevier Ltd. All rights reserved. Facile fabrication of graphene oxide/poly(styrene-co-methyl methacrylate) nanocomposite with high toughness and thermal stability Saadman Sakib Rahman a, b , Muhammad Arshad b , Muhammad Zubair b , Morteza Ghasri-Khouzani a , Ahmed Qureshi a , Aman Ullah b, * a Department of Mechanical Engineering, University of Alberta, Edmonton, AB, T6G 1H9, Canada b Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada A R T I C L E INFO Keywords: Graphene oxide Monomer ration optimization in situ bulk polymerization mechanical properties thermal stability ABSTRACT Graphene and related nanomaterial-based polymer composites have shown the potential to resolve the long- standing confict between strength and toughness, the two vital mutually exclusive mechanical properties. The uniform dispersion of the nanofllers in polymer matrices to attain strong matrix-fller interfacial bonding, which is essential for effective load transfer between the polymer matrix and fllers, is the least investigated aspect and a major challenge in composite engineering. Copolymeric materials can be exploited to enhance the distribution of nanofllers. Herein the optimization of monomer ratios of the poly (styrene-co-methyl methacrylate) copolymer and a facile method to fabricate graphene oxide (GO) reinforced nanocomposites using in situ bulk copoly- merization are reported. The ultimate tensile strength, failure strain, and storage modulus of the injection molded copolymer were increased by 14.6, 15, and 43%, respectively, by adding only 0.1 wt.% GO. Also, the thermogravimetric analysis revealed that the thermal stability of the nanocomposite is much better than the neat copolymer. Crack arresting mechanism and dispersion state of GO sheets in the copolymer matrix were also investigated using scanning and transmission electron microscopes. Thus, this paper provides a methodology for uniform dispersion of GO in copolymeric materials to attain high toughness and thermal stability. 1. Introduction Graphene is a fat monolayer of carbon atoms tightly packed in a two-dimensional honeycomb lattice [1]. A great deal of effort has been made to develop lightweight, strong, and tough graphene-reinforced composite materials owing to the exceptional physical properties of graphene. For instance, Young’s modulus near 1 TPa and almost 100 times greater tensile strength (130 GPa) than steel [2], thermal con- ductivity above 3000 Wm -1 K -1 [3], complete impermeability to gases [4], and extremely high specifc surface area [5]. However, due to the large aspect ratio, van der Waals, and π-π interactions, exfoliated gra- phene layers have a strong tendency to aggregate and phase separate, resulting in poorly dispersed bundles and agglomerates in polymer-matrix [6]. Nevertheless, one fundamental property of gra- phene is that it can be chemically functionalized by oxygen-containing groups such as epoxy, hydroxyl, carbonyl, and carboxylic acid group- s—this oxidized form of graphene is known as graphene oxide (GO). The hydrophilicity-hydrophobicity balance of GO, ability to dissolve and form stable colloid solutions in water and a wide range of organic sol- vents, and better interfacial-bonding capabilities of its functional groups—attached to the basal plane and edges—with polymer-matrix, made GO a promising candidate for fller-reinforced polymer composites. As reported in recent works of literature, the addition of GO in polymer matrices leads to considerable improvements of not only the mechanical properties including strength, toughness, stiffness, and hardness but also the viscoelastic and thermal properties of the virgin polymers [7–13]. Solution blending, melt blending, and in situ poly- merization are the three main methods to prepare GO-based polymer nanocomposites [14]. The homogeneous dispersion and exfoliation of GO sheets in polymer matrices are diffcult to achieve in the case of melt blending due to the high viscosities of polymer melts. Besides, GO sheets undergo in situ thermal reduction and lose oxygen-containing functional groups, which leads to a weak interaction between GO sheets and polymer chains, and as a consequence, inferior mechanical properties are observed [15]. Also, melt blending of two immiscible polymers in * Corresponding author. E-mail address: ullah2@ualberta.ca (A. Ullah). Contents lists available at ScienceDirect Materials Today Communications journal homepage: www.elsevier.com/locate/mtcomm https://doi.org/10.1016/j.mtcomm.2020.101633 Received 16 July 2020; Received in revised form 30 August 2020; Accepted 4 September 2020