Jae Whan Cho

Graphene oxide (GO) was functionalized with hyperbranched polyurethane (HBPU) via click coupling between azide‐functionalized HBPU and alkynyl‐decorated GO. HBPU‐functionalized GO composites of various compositions were prepared. The azide‐containing HBPU was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. The HBPU‐functionalized GO composites were characterized using transmission electron microscopy and FT‐IR spectroscopy. The functionalized GO showed excellent dispersion in the HBPU matrix, giving composites with enhanced mechanical and thermal properties. The material properties were effectively regulated by click‐coupled exfoliation of GO with HBPU, enabling the production of high‐performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44631.

A facile click chemistry approach to the functionalization of three‐dimensional hyperbranched polyurethane (HPU) to graphene oxide (GO) nanosheets is presented. HPU‐functionalized GO samples of various compositions were synthesized by reacting alkyne‐functionalized HPU with azide‐functionalized GO sheets. The morphological characterization of the HPU‐functionalized GO was performed using transmission electron microscopy and its chemical characterization was carried out using Fourier transform‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy. The graphene sheet surfaces were highly functionalized, leading to improved solubility in organic solvents, and consequently, enhanced mechanical, thermal, and thermoresponsive and photothermal shape memory properties. The strategy reported herein provides a very efficient method for regulating composite properties and producing high performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43358.

We report novel laser-heated electrospinning of poly(ethylene terephthalate) (PET) nanofibers including multi-walled carbon nanotubes (MWNTs) for enhanced mechanical properties. Laser-heated electrospinning was carried out by irradiating the fluid jet stream with a near-infrared laser during electrospinning of a PET/MWNT solution. The laser-heated electrospun nanofibers exhibited a smaller diameter than the electrospun nanofibers without laser heating, and significantly enhanced mechanical properties. The breaking stress and modulus values were higher than those of the electrospun nanofibers without laser heating, and the highest values were obtained at a laser power density of 2.5 W cm⁻². This enhancement in the mechanical properties of nanofibers is ascribed to the increased orientation of both the MWNTs and PET chains along the nanofiber axis, as shown in the polarized Raman spectroscopy measurements. The orientation of the MWNTs due to laser heating was more dominant than the orientation of the PET chains. However, the laser-heated electrospun nanofibers did not show any crystalline peaks in the X-ray diffraction measurements. Laser-heated electrospinning has significant potential for generating carbon nanotube-including nanofibers with smaller diameters and enhanced mechanical properties.

Conducting polyaniline nanofiber-grafted graphene oxide (PANINF-GO) hybrids were prepared by click coupling of azide-functionalized GO (GO-N₃) with aniline monomer-functionalized GO (GO-f-aniline) and then in situ rapid mixing polymerization in the presence of aniline. The successful synthesis of the PANINF-GO hybrids was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The chemical and electronic structures of polyaniline and GO could be largely preserved during covalent grafting via click chemistry, which was attributed to the enhanced electrical properties of the hybrids. High resolution transmission electron microscopy and scanning electron microscopy observations showed that the polyaniline was embedded on the GO surface in the form of a fibrous morphology with covalent bonding. The click coupled hybrids of PANINFs and GO in this study demonstrated excellent electrochemical properties and high stability over repeated cycles.