Toughness Enhancement in Polyactide Nanocomposites with Swallow-Tailed Graphene Oxide

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Toughness Enhancement in Polyactide Nanocomposites with Swallow-Tailed Graphene Oxide Jing Lia, Huige Yanga, Hao Wanga, Juzhong Zhanga, Shuiren Liua, Xuying Liua,*, Wentao Liua, Li Zhang a, Mingjun Niua,**, and Jinzhou Chena aSchool

of Materials Science and Engineering, The Key Laboratory of Material Processing and Mold of Ministry of Education, Henan Key Laboratory of Advanced Nylon Materials and Application, Zhengzhou University, Zhengzhou, China *e-mail: [email protected] **e-mail: [email protected] Received March 6, 2020; revised May 31, 2020; accepted June 9, 2020

Abstract—Graphene oxide modified with long flexible hydrocarbon chains attracts increasing interest in toughing and stabilizing polymer nanocomposites. Herein, graphene oxide bearing with two types of long alkyl chains, namely 2-octyldodecylamine (swallow tail) and dodecylamine (linear), were prepared and introduced into polylactide by a master batch melt blending process. Swallow-tailed graphene oxide sheets show a homogeneous and stable dispersion in organic solvents, suggesting that the bulky groups enable to weaken Van der Waals forces, which is in consistence with the increment of 4.4 Å in interlayer spacings. Moreover, 2-octyldodecylamine-functionalized graphene oxide sheets allow polyactide to be highly toughness without sacrificing tensile strength. In comparison to neat polylactide, the polylactide nanocomposites with 0.3 wt % 2-octyldodecylamine-functionalized graphene oxide display about 400% increase in the elongation at break. The crystallization properties of polylactide were also improved with nanofillers. In addition, the polylactide nanocomposites exhibit high thermal stability in the presence of 0.3 wt % swallow-tailed graphene oxide sheets. Therefore, this study provides a new concept to modify graphene oxide to elevate the dispersion of graphene oxide, which contributes to enhancing interfacial interaction and consequently endowing polymer nanocomposites with high toughness and high stability. DOI: 10.1134/S1560090420050085

INTRODUCTION Polylactide (PLA), as a biobased and biodegradable polymer, has aroused wide-spread interest in the field of biomedical applications, food packaging materials, environmental remediation, fibers and textiles, due to its renewability, biocompatibility, high mechanical strength, and high melting temperature [1–4]. However, the various applications of PLA are still limited because of its potential drawbacks such as its inherent brittleness, low crystallization degree and poor thermal stability [5, 6]. Therefore, some strategies have been proposed to improve the practical applications of PLA, including chemical copolymerization, plasticization and polymer blending [7–10]. For instance, physical blending with nanoscale particles, such as layered silicate [11], nanoclay [12], cellulose nanofiber [13, 14], or carbon nanotubes [15, 16] is also an effective strategy to improve the physical properties of PLA. These nanoscale strategies allow for the significant development of next-generation mater