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Renaissance of the Plastic Age

Renaissance of the Plastic Age. T.P.Radhakrishnan School of Chemistry, University of Hyderabad Hyderabad 500 046, India tprsc@uohyd.ernet.in http://chemistry.uohyd.ernet.in/~tpr/. Polymers for Electronics & Photonics. This file is available at http://chemistry.uohyd.ernet.in/~ch521/.

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Renaissance of the Plastic Age

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  1. Renaissance of the Plastic Age T.P.Radhakrishnan School of Chemistry, University of Hyderabad Hyderabad 500 046, India tprsc@uohyd.ernet.in http://chemistry.uohyd.ernet.in/~tpr/ Polymers for Electronics & Photonics This file is available at http://chemistry.uohyd.ernet.in/~ch521/

  2. Stone age (Before 5000 BC) Copper age (5000 - 3000 BC) Bronze age (3000 - 800 BC) Iron age (800 BC - 40 AD) Materials and civilisation Plastic age ?

  3. Biomaterials Semiconductors Composites Types of materials Metals / Alloys * Ceramics Polymers Molecular materials *Courtsey: W. D. Callister, Fundamentals of Materials Science and Engineering

  4. Chemical / Physical routes Elements / Compounds Materials Elements / Compounds Molecules Thin films / LB films Polymers Crystals Nanostructures Chemical routes Chemical / Physical routes Design of Molecular Materials

  5. Natural polymers

  6. Polytetrafluoroethylene (Teflon) Polyethylene Phenol-formaldehyde (Bakelite) Polyhexamethylene adipamide (Nylon 6,6) Polycarbonate Polyethyleneterephthalate (PET) Synthetic polymers

  7. Acetylene gas Ti(OBu)4 & Et3Al Toluene –78oC Ti(OBu)4 & Et3Al Hexadecane 150oC silvery film trans-polyacetylene Discovery of conducting polymers 1862 Lethby (College of London Hospital) Oxidation of aniline in sulfuric acid 1970’s Shirakawa (Japan) copper-coloured film cis-polyacetylene

  8. Polyacetylene (PA) Electrical conductivity (s) cis PA 10-10 – 10-9 S cm-1 trans PA 10-5 – 10-4 S cm-1 For comparison : s (copper) ~ 106 S cm-1 : s (teflon) ~ 10-15 S cm-1

  9. Semiconductor s ~ 10-5 S cm-1 - e- + e- Metal s ~ 104 S cm-1 Doping leads to enhanced conductivity

  10. Discoverers - Nobel Prize 2000 A. Heeger, A. McDiarmid, H. Shirakawa (this photograph taken at the International Conference on Synthetic Metals, 2000, was kindly provided by Prof. Heeger)

  11. Polyacetylene - electronic structure -electronic energy levels and electron occupation (d) regular trans-PA (e) dimerised trans-PA (a) ethylene (b) allyl radical (c) butadiene

  12. How does a conducting polymer work ? Oxidative doping of polyacetylene by iodine Polaron and its delocalisation

  13. Bipolaron Neutral Soliton Positive Soliton Excitations

  14. Examples of conducting polymers

  15. Copper 10+6 Platinum Bismuth 10+4 Graphite 10+2 100 Germanium Conducting Polymers 10-2 10-4 Silicon 10-6 10-8 10-10 10-12 Diamond 10-14 10-16 Quartz S cm-1 10-18 Electrical conductivities Polyethylene

  16. Cathode Anode (ITO plate) Aniline + dil. HCl Synthesis of PANI Instead of electrochemical oxidation, chemical oxidation may be carried out : Aniline + acid + oxidising agent ((NH4)2S2O8)

  17. Voltage (~ 0.3 - 0.5 V) applied

  18. Result of electropolymerisation The green coating on the ITO electrode is due to the formation of emeraldine salt form of PANI

  19. Leucoemeraldine Colorless (Insulator) Emeraldine base Blue (Insulator) Emeraldine salt Green (Conductor) Purple (Insulator) Pernigraniline Polyaniline (PANI) Oxidation

  20. Applications of conducting polymers Polyaniline (PANI) Transparent conducting electrodes Electromagnetic shield Corrosion inhibitor ‘Smart windows’ (electrochromism) Polypyrrole (Ppy) Radar-invisible screen coating (microwave absorption) Sensor (active layer) Polythiophene (PT) Field-effect transistor Anti-static coating Hole injecting electrode in OLED Polyphenylenevinylene (PPV) Active layer in OLED

  21. Polypyrrole - conductivity switching

  22. Enzyme Biosensor Using PPy Glucose oxidase -D-glucose + ½O2 + H2O  D-gluconic acid + H2O2 H2O2 + 2HCl + Ppy  2H2O + Ppy2+.2Cl-

  23. PANI-PSS PSSn-(100 kDa) RT = 8.3x10-2 Scm-1 PSSn-(70 kDa) RT = 3.6x10-2 Scm-1 PSSn-

  24. Ammonia in Ammonia out Sensors Typical example : Ammonia sensing by PANI-PSSM film Resistance change with time

  25. Resistance change at 150 sec. for different concentrations of ammonia

  26. - Metal electrode Electric field Organic thin film + Transparent electrode (ITO) Light Electroluminescence

  27. e- LUMO LUMO h+ HOMO HOMO Light Cathode Anode Principle of EL

  28. Polymers for Organic Light Emitting Diodes (OLED) PPV MEH-PPV Commercial materials like Mn2+ in ZnS require 100V DC PPV : requires 5 - 10V DC runs even with AC brightness ~40,000 cd/m2 ie. ~100 times brighter than a TV screen

  29. D S Ca/Ag MEH/PPV Silica Gold P3HT Silica n+-Silicon Aluminium G Organic LED driven by organic transistor

  30. V Li anode Polymer electrolyte Conducting polymer Polymer Undoped Doped Polythiophene RedBlue Polypyrrole Yellow-greenBlue-black Polyaniline YellowGreen/Blue ITO electrode Viewing side Electrochromic devices

  31. V Li anode Polymer electrolyte Conducting polymer ITO electrode Viewing side On application of voltage

  32. ( ) Polydiacetylene n Conjugated polymers for nonlinear optics NLO materials interact with light Light changes the material properties Changes the properties of the light

  33. Laser 1 No light Polariser Crossed Polariser NLO (c(3)) polymer Laser 2 Laser 1 Polariser Crossed Polariser Photonic Application of Conducting Polymers - Kerr gate

  34. Future Outlook All organic transistor

  35. Plastic solar cell based on MDMO-PPV/PCBM (conducting polymer - fullerene composite) on flexible ITO coated PET

  36. Thank you

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