Sibdas Singha Mahapatra

Highly stretchable, transparent and scalable elastomers with tunable dielectric permittivity

We report a fast and simple process for the large scale fabrication of highly flexible, optically transparent carbon nanotube composites with massive dielectric permittivity. Various concentrations of pristine SWNTs were dispersed in hyperbranched polyurethane to prepare uniformly dispersed nanocomposite materials. Our solution-based method does not require modification on the carbon nanotubes, thus preserving the intrinsic electronic and high mechanical properties of the composites.

The synergistic effect of the combined thin multi-walled carbon nanotubes and reduced graphene oxides on photothermally actuated shape memory polyurethane composites

We evaluated the synergistic effect of the hybrid-type nanocarbon, consisting of 1D thin-walled carbon nanotubes (TWNTs) and 2D reduced graphene oxide (RGO), on the shape memory performance of hyperbranched polyurethane composites. The shape recovery of the resulting composites was activated via a photothermal process using a near-infrared laser. The best laser-induced shape recovery performance was achieved for the composites with a 7/3 of TWNT/RGO ratio and a 1wt.% of nanocarbon content. Such result can be explained by good dispersion of TWNTs and RGO in the hyperbranched polymer as well as three-dimensionally enhanced interconnection between carbon nanotubes and graphenes. The optically active TWNTs with a high optical absorption section exhibited high ability of transferring laser-induced thermal energy to polymer matrix whereas RGO provided a high mechanical property to polymer matrix. The tensile modulus and electrical conductivity of the composites also showed a similar dependence on the TWNT/RGO composition ratio as the photothermal shape recovery. Our study demonstrated an effective conversion from light, thermal to mechanical work by irradiating shape memory polymer composite containing hybrid-type fillers using a near-infrared laser.

Soluble conducting polymer-functionalized graphene oxide for air-operable actuator fabrication

An effective route for the preparation of a processable, conducting polymer-functionalized graphene oxide for actuator applications is investigated. First, graphene oxide (GO) is covalently functionalized with a 3-thiophene acetic acid (TAA) monomer by an esterification reaction. Then, the TAA-functionalized GO is self-polymerized by chemical oxidative polymerization to yield poly(3-thiophene acetic acid)-functionalized GO (GO-f-PTAA). Further, the GO-f-TAA is also copolymerized with thiophene (Th) to yield GO-f-PTAA-co-PTh. The synthesis of GO-f-PTAA and GO-f-PTAA-co-PTh composites is confirmed by Fourier transform infrared, 1H-nuclear magnetic resonance, and X-ray photoelectron spectroscopies. The composites show better electrochemical properties than pure PTAA and superior solubility in organic solvents compared to pure GO. Using the soluble GO-f-PTAA and GO-f-PTAA-co-PTh composites, air-operable actuators are fabricated and their actuation performance is investigated. The copolymer-functionalized GO actuator exhibits good electroactive actuation behavior between 2 and 4 V, mainly because of the enhanced electrochemical performance of the composites, whereas the pure PTAA and GO-f-PTAA actuators do not show actuation under the applied voltage. The soluble conducting polymer-functionalized graphene composites developed in this study have potential applications in the fabrication of actuators that can be operated in air.

A reactive graphene sheet in situ functionalized hyperbranched polyurethane for high performance shape memory material

A new and facile route has been developed to prepare graphene oxide (GO) reinforced hyperbranched polyurethane (HPU) composites by in situ polymerization technique. To increase the reactivity of GO during in situ polymerization, the aliphatic hydroxyl groups are decorated on the surface of graphene sheets. The enhanced grafting was confirmed by Fourier-transform infrared spectra and high resolution transmission electron microscopy. The high grafting yield of 84% was obtained from thermogravimetric analysis after removing the non-attached HPU from the composites. The covalently bonded graphene sheets with hyperbranched polyurethane were homogeneously dispersed due to grafted HPU-assisted dispersion in the pure polymer matrix. In comparison with pure hyperbranched polyurethane, the highly flexible graphene-based shape memory polyurethane composite exhibited higher modulus and breaking stress, and exceptional elongation-at-break. The resulting composite exhibited 98% shape recovery, 93% shape retention, and enhanced thermal stability; thus, it would be a promising material for the fabrication of graphene-based actuating devices. Consequently, this simple protocol has great potential in the preparation of various high-performance polymer composites.

Functionalization of graphene with self-doped conducting polypyrrole by click coupling.

The synthesis of self-doped conducting polypyrrole-grafted graphene sheets (GS-PPy) for non-volatile memory applications is reported. First, the alkyne-modified graphene sheets (GS-alkyne) were covalently functionalized with a water-soluble polymer containing numerous anionic SO3(-) dopants by a copper-catalyzed click reaction. Then, polypyrrole was covalently grafted onto the functionalized graphene sheets by chemical oxidative polymerization to produce GS-PPy hybrids. The GS-PPy hybrids showed a uniform coating of PPy on the GS sheets, good dispersion in aqueous solutions, high electrical conductivity, and red-shifted absorption peak in the UV/Visible spectra. The non-volatile memory device composed of a Al/(GS-PPy/poly(vinyl alcohol))/Al structure, produced by spin coating of the aqueous GS-PPy/poly(vinyl alcohol) solution, showed a good write-once read-many times memory behavior, which was due to good electrical and optical absorption properties of the GS-PPy hybrids. The findings of this study provide a potential solution for the fabrication of water-soluble graphene-based hybrids for non-volatile resistive-memory-based applications.

Synthesis and electrochemical properties of conducting polyaniline/graphene hybrids by click chemistry

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.

Synthesis of calix[4]arene-segmented polyurethane and its nanocomposites with single-walled carbon nanotubes

Calix[4]arene-segmented polyurethane (CPU) was synthesized in a two-step reaction. The synthesis of CPU was confirmed by measurements of FT-IR and 1H-NMR spectroscopy. The CPU nanocomposites with single-walled carbon nanotubes (SWCNTs) showed non-agglomerated homogeneous dispersion of SWCNTs in the CPU matrix according to field emission scanning electron microscope measurements. The mechanical properties of the CPU were enhanced by incorporation of the SWCNTs due to the nano-reinforcement effect of the SWCNTs and the long-range structure of the polymer. It has been demonstrated that these CPU-SWCNT nanocomposites possess the robust mechanical and thermal behavior.

Synthesis and characterisation of poly(3-hexyl thiophene)-grafted graphene oxide sheets by click chemistry

Poly(3-hexyl thiophene)-grafted graphene oxide (GO-f-P3HT) was synthesised via two kinds of click chemistry reaction owing to different synthesis methods of azide-functionalised GO, that is, azide-functionalised GO derived from 2-chloroethyl isocyanate-treated GO (GO-f-P3HT(1)) and azide-functionalised GO by direct conversion of epoxy groups in the GO to azide groups (GO-f-P3HT(2)). The successful covalent grafting of P3HT to GO in both samples of GO-f-P3HT(1) and GO-f-P3HT(2) was confirmed by Fourier transform infrared and X-ray photoelectron spectroscopies. The transmission electron microscopy (TEM) measurements showed clearly that the P3HT molecules were present on the surface of GO sheets. In addition, it was observed that more polymer chains were attached on the GO surface of GO-f-P3HT(1) owing to more favourable click chemistry reaction in GO-f-P3HT(1) than GO-P3HT(2). The click coupling in this study was found to be effective for achieving homogeneous dispersion of GO in P3HT molecules which is desired for high performance P3HT-based electronic devices.

Fabrication and characterization of dry conducting polymer actuator by vapor phase polymerization of polypyrrole.

A trilayered dry conducting polymer actuator was fabricated via application of a polypyrrole (PPy) coating on both sides of a solid polymer electrolyte film using vapor phase polymerization (VPP). The solid polymer electrolyte film was prepared by incorporation of different weight ratios of dodecylbenzene sulfonic acid sodium salt in poly(vinyl alcohol) (PVA) by solvent casting. The successful polymerization of PPy was confirmed by Fourier transform infrared spectroscopy; a uniform PPy coating on the solid polymer electrolyte film surface was also observed by scanning electron microscopy. The dry PVA/PPy actuator demonstrated good actuation behavior at a low applied voltage of 1-3 V. The actuator bending displacement was found to increase with an increase in the applied voltage. The VPP approach in this study provides a very effective method for achieving a uniform polymer coating in the fabrication of a dry conducting polymer actuator.

Synthesis and Application of Conducting Polyaniline-Fe3O4 Nanohybrid by Click Chemistry Reaction

Abstract: A conducting polyaniline-Fe 3 O 4 nanohybrid was synthesized via click coupling of iron oxide nanoparticles and 2-ethynylaniline. Covalent functionalization of the azide-functionalized iron oxide nanoparticles and the 2-ethynylaniline wasconfirmed with Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy, and the coating of polyanilineon iron oxide nanoparticles was confirmed with field-emission scanning electron microscopy. The nanohybrid incorporatedinto a poly(vinyl alcohol) (PVA) matrix by solution casting showed excellent compatibility with the PVA. Consequently, themechanical properties and electrical conductivities of the resultant composite films were improved remarkably. This clickcoupling protocol offers the possibility of completely combining the extraordinary performance of nanohybrids with PVAproperties.Keywords: hybrid, click chemistry, polyaniline, electrical conductivity, mechanical properties 1. Introduction Conducting nanohybrids have potential applications foruse in sensors, actuators, batteries, light emitting diodes, andelectromagnetic interference shielding devices [1,2]. Amongthe conducting polymers, polyaniline (PANI) has received agreat deal of attention due to its good environmental stability,easy doping-dedoping by chemical means, and facile synthesis.It can be readily prepared in bulk by chemical oxidativepolymerization of aniline under controlled conditions.Compared with many other π-conjugated polymers, PANIshows sufficient stability for practical applications. Theproperties of these conducting polymers can be easilymanipulated by the incorporation of nanomaterials. It isbecause the nanoscale particles are more attractive due tointriguing properties arising from the nanosize and largesurface area [3-5]. The incorporation of nanoscale fillers can alter the physicaland electrical properties of conducting polymers. Variousmetallic and metal oxide nanosize particles have so far beeninserted into the shell of conducting polymers giving rise toa host of nanocomposites. Magnetic nanoparticles of Fe