Dramatic Enhancement of Graphene Oxide/Silk Nanocomposite Membranes: Increasing Toughness, Strength, and Young’s modulus via Annealing of Interfacial Structures

Abstract

We demonstrate that stronger and more robust nacre-like laminated GO (graphene oxide)/SF (silk fibroin) nanocomposite membranes can be obtained by selectively tailoring the interfacial interactions between "bricks"-GO sheets and "mortar"-silk interlayers via controlled water vapor annealing. This facial annealing process relaxes the secondary structure of silk backbones confined between flexible GO sheets. The increased mobility leads to a significant increase in ultimate strength (by up to 41%), Young's modulus (up to 75%) and toughness (up to 45%). We suggest that local silk recrystallization is initiated in the proximity to GO surface by the hydrophobic surface regions serving as nucleation sites for β-sheet domains formation and followed by SF assembly into nanofibrils. Strong hydrophobic-hydrophobic interactions between GO layers with SF nanofibrils result in enhanced shear strength of layered packing. This work presented here not only gives a better understanding of SF and GO interfacial interactions, but also provides insight on how to enhance the mechanical properties for the nacre-mimic nanocomposites by focusing on adjusting the delicate interactions between heterogeneous "brick" and adaptive "mortar" components with water/temperature annealing routines.

Role of Interface Interactions in the Construction of GO‐Based Artificial Nacres

“…[51,58,90] Figure 2 shows that in the past decade, an increasing research effort has been made to improve the mechanical properties of graphene-based nanocomposites by various interfacial www.advmatinterfaces.de modifications. [48,75,[91][92][93][94] The interfacial crosslinking strategies contain hydrogen bonding, [95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114] ionic bonding, [81,[115][116][117][118] π-π interaction, [119][120][121] and covalent bonding. Inspired by nacre, a vast variety of highperformance GO-based nanocomposites and their reduced counterparts, including 1D fibers, 2D films, and 3D bulk materials, have been successfully constructed by interfacial crosslinking and building block toughening.…”

“…Various molecules, including small solvent molecules, [104,145,146] linear polymers, [102,104,110,113,[147][148][149] branched polymers, [111] and biomacromolecules, [96,105,106,114,150] could be used to construct hydrogen bonding between adjacent GO nanosheets. Various molecules, including small solvent molecules, [104,145,146] linear polymers, [102,104,110,113,[147][148][149] branched polymers, [111] and biomacromolecules, [96,105,106,114,150] could be used to construct hydrogen bonding between adjacent GO nanosheets.…”

“…However, the dense hydrogen bonding network restricts the deformation of HPG, thereby resulting in lower tensile strain (≈3.7%) than pure GO fiber (≈6.8-10.1%). [164] Compared with the synthesized polymers, the biomacromolecules, such as konjac glucomannan [114] and silk fibroin (SF), [96,105,106,150] have the advantage of providing large plastic deformation due to the complex multilevel spatial structure. [164] Compared with the synthesized polymers, the biomacromolecules, such as konjac glucomannan [114] and silk fibroin (SF), [96,105,106,150] have the advantage of providing large plastic deformation due to the complex multilevel spatial structure.…”

Combined Application of Graphene‐Family Materials and Silk Fibroin in Biomedicine

“…With increasing concentration of graphene‐family materials, the content of silk II structure (β‐sheet) in composites increased, without any evidence of a downward trend ,. The mechanical properties of the composite materials were also increased significantly at higher concentrations of graphene‐family materials within the specified range ,. A recent study showed that the secondary structure of SF chains adsorbed on GO was also highly dependent on the pH level, leading to different changes in the composites’ properties .…”

Robust and Flexible Micropatterned Electrodes and Micro‐Supercapacitors in Graphene–Silk Biopapers

“…Much work has also focused on the assembly of nanocomposites, whereby GO acts as 2D “bricks” bound by 1D polymeric binders to yield nacre‐like structures designed for superior mechanical properties, including extreme tensile strength (526.7 MPa in GO–chitosan), Young's modulus, toughness (13.9 MJ m −3 reduced graphene oxide–silk fibroin, GO–SF), and stretchability (up to 10.1% in GO–polyvinyl alcohol) . Synergistic effects arise from confined networks of intermolecular interactions to produce materials with superior mechanical properties in composites otherwise comprised of soft constituent components . However, the investigation of layered graphene composites has been largely confined to structural applications .…”