On the Effect of Ultralow Loading of Microwave-Assisted Bifunctionalized Graphene Oxide in Stereolithographic 3D-Printed Nanocomposites

Edgar-Homero Ramírez-Soria; José Bonilla-Cruz; Monica Gabriela Flores-Amaro; Vincent Joseph García; Tania E Lara-Ceniceros; Francisco E Longoria-Rodríguez; Perla Elizondo; Rigoberto C Advincula

doi:10.1021/acsami.0c13702

On the Effect of Ultralow Loading of Microwave-Assisted Bifunctionalized Graphene Oxide in Stereolithographic 3D-Printed Nanocomposites

ACS Appl Mater Interfaces. 2020 Oct 28;12(43):49061-49072. doi: 10.1021/acsami.0c13702. Epub 2020 Oct 19.

Affiliations

¹ Advanced Functional Materials & Nanotechnology Group, Centro de Investigación en Materiales Avanzados S. C. (CIMAV-Unidad Monterrey), Av. Alianza Norte 202, Autopista Monterrey-Aeropuerto Km 10, PIIT, C.P. 66628 Apodaca-Nuevo León, México.
² Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León (UANL), AP 1864, 64570 Monterrey-Nuevo León, México.
³ Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States.
⁴ University of Tennessee, Knoxville, Tennessee 37996, United States.
⁵ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States.

PMID: 33073976
DOI: 10.1021/acsami.0c13702

Abstract

Surface functionalization of graphene oxide (GO) is one of the best ways to achieve homogeneous dispersions of GO within polymeric matrices and composites. Nonetheless, studies regarding how the level of GO functionalization affects the macroscopic properties of three-dimensional (3D) printed nanocomposites are still few. Furthermore, the bifunctionalization of GO with the NH₂/NH₃⁺ groups to obtain improved thermomechanical macroscopic properties at ultralow loads has not been reported. In this paper, fast and straightforward surface bifunctionalization of GO with a controlled ratio of NH₂/NH₃⁺ groups at low, medium, and high functionalization levels (AGOL, AGOM, and AGOH) in a one-step microwave-assisted synthesis is reported for the first time. The functionalization mechanism was disclosed, wherein three graft densities (G_φ) were obtained. A plateau of maximum functionalization (G_φ = 4.9 μmol/m² = 2.9 molecules/nm²) was reached, suggesting that full coverage of the GO surface is achievable. Also, an increase in the exfoliation of functionalized layers was obtained, ranging from d₀₀₂ = 8.6 Å up to d₀₀₂ = 15.8 Å. X-ray photoelectron spectroscopy (XPS) reveals the successful functionalization of GO, as well as an atomic relationship NH₂/NH₃⁺ of about 50/50% in all functionalized samples. Stereolithographic (SLA) 3D-printed nanocomposites (AGOL/R, AGOM/R, and AGOH/R) were obtained using ultralow loads (0.01 wt %) of each bifunctionalized material. This ultralow amount was sufficient to enhance thermal stability (up to 4 °C) and a significant increase in the glass transition temperature (93 °C ≤ T_g ≤ 120 °C). Interestingly, we found that low and medium grafting density promotes a ductile material (ε > 5%); meanwhile, a high graft density produces brittle materials. Also, we observe that the toughness can be tuned as a function of the graft density (AGOH: 24 MPa, AGOM: 342 MPa, AGOL: 562 MPa) at ultralow loadings. The 3D-printed nanocomposites using GO with low graft density (AGOL) increase their tensile strain by 90% in comparison with the control sample (without filler). Finally, the underlying mechanisms were discussed to explain the findings.

Keywords: 3D printing; bifunctionalization; ductile−brittle nanocomposites; graphene oxide; toughness.