title: Graphene-Induced Oriented Interfacial Microstructures in Single Fiber Polymer Composites.
abstract: Interfacial interactions between the polymer and graphene are pivotal in determining the reinforcement efficiency in the graphene-enhanced polymer nanocomposites. Here, we report on the dynamic process of graphene-induced oriented interfacial crystals of isotactic polypropylene (iPP) in the single fiber polymer composites by means of polarized optical microscopy (POM) and scanning electron microscopy (SEM). The graphene fibers are obtained by chemical reduction of graphene oxide fibers, and the latter is produced from the liquid crystalline dispersion of graphene oxide via a wet coagulation route. The lamellar crystals of iPP grow perpendicular to the fiber axis, forming an oriented transcrystalline (TC) interphase surrounding the graphene fiber. Various factors including the diameter of graphene fibers, crystallization temperature, and time are investigated. The dynamic process of polymer transcrystallization surrounding the graphene fiber is studied in the temperature range 124-132 °C. The Lauritzen-Hoffman theory of heterogeneous nucleation is applied to analyze the transcrystallization process, and the fold surface free energy is determined. Study into microstructures demonstrates a cross-hatched lamellar morphology of the TC interphase and the strong interfacial adhesion between the iPP and graphene. Under appropriate conditions, the β-form transcrystals occur whereas the α-form transcrystals are predominant surrounding the graphene fibers.
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: John P
authors.initials: JP
authors.lastname: Abdou
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Braggin
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: Yanqi
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: Alexandra R
authors.initials: AR
authors.lastname: Stevenson
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: Danielle
authors.initials: D
authors.lastname: Chun
authors.affiliation: Department of Chemistry and Biochemistry, California Polytechnic State University, 1 Grand Avenue, San Luis Obispo, California 93407, United States.
authors.forename: Shanju
authors.initials: S
authors.lastname: Zhang
keywords: adhesion; crystallization kinetics; fibers; graphene; interfacial interactions; polymer composites