Chemical synthesis of conducting polymer nanofibers

1. Leuco-Emeraldine Base Leuco-Emeraldine Salt Emeraldine Salt (Organic Metal) Chemical synthesis of conducting polymer nanofibers for H2 storage applications A. R. Phani1*, S. Santucci1,2, S. Srinivasan3, and E. Stefankos3 1 NANO-Center for Advanced Technologies S.r.l, Department of Physics - University of L’Aquila, via Vetoio 10, 67010 Coppito, L’Aquila – Italy 2 CASTI, CNR-INFM Regional Laboratory, and Department of Physics - University of L’Aquila, via Vetoio 10, 67010 Coppito, L’Aquila – Italy 3 CERC, Department of Electrical Engineering, University of South Florida, Tampa, USA University of L’Aquila Industrial and Commercial Applications of polyaniline Motivation • Nanofibers with diameters of tens of nanometers appear to be an intrinsic morphological unit that was found to “naturally” form in the early stage of chemical oxidative polymerization of aniline. • Based on this, two methods – interfacial polymerization and rapidly mixed reactions-have been developed that can readily produce pure nanofibers by slightly modifying the conventional chemical synthesis of polyaniline without the need for any template or structural directing material. With this nanofiber morphology, dispersibility and processbility of polyaniline are now much improved. • In the present investigation, highly rough, and large surface area polyaniline nanofibers have been grown by using a template process using camphorosulfonic acid. Morphological, structural, optical properties have been investigated. • Conducting polymer nanostructures combine the advantages of organic conductors and low dimensional systems and therefore should yield many interesting physicochemical properties and useful applications. The nanofibrillar morphology significantly improves the performance of polyaniline in many conventional applications involving polymer interactions with its environment. This leads to much faster and more responsive chemical sensors, new organic / polyaniline nanocomposites and ultra-fast non volatile memory devices. • Effect of surfactants on the formation of polyaniline nanofibers morphology, structure has been systematically investigated. Experiments are under conducted to store H2 in the polyaniline nanofibers, nanospheres and plausible mechanism has been explained. • Polyaniline is a conducting polymer for a variety of applications such as • Neat materials, Blends, Compounds • Electrostatic discharge protection materials • Packaging Industry • Gas sensors • Solar cells, Electronics • Fenestration (Electrochromic smart windows) • Textile and Automotive Industry • Construction and Mining • Building services (Smart windows) • Transportation • Chemical additives, Textile, Food • Plastic processing • Electroactive inks • Fire extinguishing agents • Hydrogen storage • Electrical insulators • Paints, Chemical Sensors • Corrosion protection, Welding • Antistatic packaging material • Printed Circuit Boards • Conductive pipes for explosives • Non-linear optics Chemical Structure • Advantages of Polyaniline • Wide controllable range of conductivity • Melt and solution process able material • Conductive Blends with many commodity polymers • Function as processing aids in addition to conductivity • Colour and transparent electrically conductive products Flowchart for the preparation of polyaniline Flowchart for the preparation of polyaniline Scanning Electron Microscopy Images XRD and UV CSA CSA -15h Nanofibers Chemical Process Aniline monomer + 5M HCl (Stirred and cooled to 0°C) Ammonium persulfate + 5M HCl (Stirred and cooled to 0°C) CSA CSA – 45h Stirred and cooled to 0°C for 5h Camphorosulfonic acid CSA – 90h CSA Monomer : aniline Oxidizer : ammonium persulfate Surfactants : PVP, Triton 100X, CTAB, and CSA Stirred at 0°C for 15h Filtered and washed with DI H2O and CH3OH • Surfactants Camphorosulfonic acid and with equivalent moles of aniline and oxidizer ammonium persulfate (1 mole) and 0.25 moles of surfactants have formed complete formation of nanofibers with diameter 80 - 150 nm. • The peak centered at 2 = 22 could be caused by the periodicity parallel to the polymer chain, whereas the peak around 2θ = 27° is attributed to the periodicity perpendicular to the direction of polymer chain. All the obtained nanofibers are amorphous. • The strong -* peak at 330 nm corresponds to benzeniod transition, another strong -* peak peak 630 nm corresponds to bezenoid to quinoid transition indicating the synthesized polymer is polyaniline in oxidized form. Annealed at 100°C for 1h Characterization XRD, FTIR, UV, BET, DTA, SEM Testing of H2 storage (under different condition) Life cycle Kinetics at RT Kinetics in different cycles at RT Isotherms at RT Hydrogen sorption kinetics at room temperature from 14th cycle to 25th cycle. No degradation in the capacity is observed. Pressure-Composition-Temperature (sorption isotherms) of PANI-NF at room temperature (2nd – 6th cycle); Plateau pressure of 30 bars is clearly seen in the 2nd absorption PCT and it reduces in the subsequent cycles. Hydrogen absorption and desorption kinetics of PANI-NF in initial (1st) and 13th cycle Conclusions • We report for the first time the reversible hydrogen storage behavior at room temperature in polyaniline (PANI) nanofibers synthesized by chemical templating technique. • The rate of hydrogen sorption during the initial run shows very rapid, i.e. 95% hydrogen storage capacity (~3-4 wt.%) absorbed in 5-6 min. • Moreover, these PANI nanofibers demonstrate excellent reversibility (up to 25 cycles) at room temperature. Another important feature discernible from the PCT (Pressure-Composition-Temperature) isotherms is that during the second hydrogen absorption run, the plateau pressure occurred around 30 bars, and it reduces in subsequent cycles. • Nevertheless, the reversible capacity of ~3-4 wt.% was maintained through out 25 cycles. The structural and surface area profiles of PANI nanofibers before and after hydrogenation and dehydrogenation cycles shows not much change as observed from XRD and BET analysis. However, there is a change in the microstructural behavior which confirms the effective hydrogenation. Pore size and micropore volume of PANI-NF before and after hydrogen sorption obtained from the BET measurement. Note: This work is a collaborative research with CERC, USF, USA, and an International patent is under progress * Principle Author e-mail: phani_ayala@nanocat.it 1NANO-Center for Advanced Technologies S.r.l 2Department of Physics Acknowledgement:Authors would like to thank Dr P. De Marco for SEM analysis of the samples