Conjugated Polymers

Conjugated Polymers: The Interplay Between Synthesis, Structure, and Properties.- 1. Introduction.- 2. Structural Features of Conjugated Polymers.- 3. Polymer Synthesis: Basic Methods.- 3.1 Step-Growth Polymerization.- 3.2 Chain-Growth Polymerization.- 3.3 Ring-Opening Polymerization.- 4. Direct Synthetic Methods.- 4.1 Electrochemical Synthesis.- 4.2 Synthesis by Step-Growth Polymerization.- 4.2.1 Polyaniline (PAN).- 4.2.2 Poly(Phenylene Sulfide).- 4.2.3 Polythiophene and its Derivatives.- 4.2.4 Other 5-membered Heterocyclic Derivatives.- 4.2.5 Polyparaphenylene (PPP).- 4.2.6 Polysilanes.- 4.2.7 Polymers of Phthalocyanines.- 4.2.8 Other Conjugated Metal Coordination Polymers.- 4.2.9 Ladder Polymers.- 4.3 The Unusual Topochemical Polymerization to form Polydiacetylenes.- 4.4 Chain-Growth Polymerizations.- 4.4.1 Polyacetylene via Ziegler-Natta Polymerization.- 4.4.2 Ring-Opening Metathesis Polymerization Routes to Polyacetylenes.- 5. Polymers from precursors.- 5.1 Polyparaphenylene (PPP).- 5.2 Poly(Phenylene Vinylene) (PPV) and Other Vinylene Polymers.- 5.3 Precursors to Polyacetylene.- 6. Extentions of these Methods in the Synthesis of “Small-Bandgap” Polymers.- 7. Conjugated Polymer Matrices.- 8. Conclusions and Caveats.- Acknowledgements.- References.- Properties of Highly Conducting Polyacetylene.- 1. Introduction.- 2. Sample Synthesis, Morphology and Properties.- 2.1 Standard Routes of Synthesis.- 2.2 Naarmann-Type Polyacetylene.- 3. Conductivity: Experimental.- 3.1 The Standard Four-Probe and Montgomery Techniques.- 3.2 Test of Sample Homogeneity.- 3.3 Conductivity Measurement.- 3.4 Sample Preparation.- 4. Conductivity Measurements: Experimental Results.- 4.1 General Remark.- 4.2 Temperature Dependence of ? and ??.- 4.3 Conductivity at Very Low Temperatures (14mK – 4.2 K).- 4.4 Anisotropy and Stretching Ration.- 4.5 Aging Effects in ?(T).- 4.6 Anisotropy and Aging.- 4.7 Dependence of ?(T) on the Dopant Concentration.- 4.8 Doping with FeCl3.- 4.9 Pressure Dependence.- 5. Discussion of ?(T).- 5.1 Experimental Prerequisites for a Model of Charge Transport for T > 400 mK.- 5.2 The Failure of Conventional Models.- 5.3 Description with the Sheng Formula.- 5.4 Limits of the Applicability of Sheng’s Model.- 5.4.1 Low Temperature Limit.- 5.4.2 Image Charge Correction Parameter A.- 5.4.3 Possible Temperature Dependence of ?$$\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{\infty }$$.- 5.4.4 Paasch’s Approach.- 5.5 Evaluation within a Phenomenological Model.- 5.6 Influence of the Barriers on ? (300 K).- 5.7 The Influence of Phonon Scattering on the Conductivity.- 5.8 Low Temperature Behaviour and Aging.- 5.8.1 Describing ?(T) with Sheng’s Formula.- 5.8.2 Influence of Finite Chain Lenghts.- 5.9 Conclusions.- 6. Morphology and Charge Transport.- 6.1 SEM on Freshly-Prepared Samples.- 6.1.1 Sample Preparation for SEM.- 6.1.2 Results.- 6.2 Local Density and Bulk Density.- 6.3 Geometrical and Electrical Anisotropy.- 6.4 Influence of Oxygen Aging and Iodine Doping.- 6.4.1 Oxidation by Oxygen (“Aging”).- 6.4.2 Oxidation by Iodine (“Doping”).- 6.4.3 Charging Effects.- 6.5 TEM on Individual Polyacetylene Fibrils.- 6.5.1 Experimental.- 6.5.2 Results.- 7. Conductivity Barriers and Morphology: a Comparison.- 8. Summary and Outlook.- Acknowledgements.- Literature.- Electronic Properties of Heavily Doped Trans-Polyacetylene.- 1. Introduction.- 2. Models for the Metallic State of Heavily Doped Trans-(CH)x.- 3. Methodology.- 3.1 Hamiltonian.- 3.2 Self-Consistent Calculation Scheme.- 3.3 Description of the Optimized Systems.- 3.4 Polaron Lattice.- 3.5 Density of States.- 4. Results and Discussion.- 4.1 Optimized Geometry using the Conwell-Mizes-Jeyadev Potential.- 4.2 The Effect of Intra-Chain Electron-Electron Interactions.- 4.3 Disordered System.- 4.4 Polaron Lattice.- 4.5 Evolution of the Energy Gap as a Function of Doping Level.- 4.6 Density of States.- 5. Summary and Conclusion.- Acknowledgements.- References.- Solution Processing of Conducting Polymers: Opportunities for Science and Technology.- I. Introduction.- A. Conducting Polymers: Materials with a Unique Combination of Electrical and Mechanical Properties.- B. Conducting Polymers: Approaches to Processing.- C. Blends of Conducting Polymers with Saturated Polymers.- II. Conducting Polymers in Solution.- A. Electronic Structure (and Conformation) of the Neutral Polymers in Solution.- B. Electronic Structure (and Conformation) of the Doped Polymers in Solution.- III. Electrical and Mechanical Properties of Oriented Poly(3-alkylthiophenes) Processed from Solution.- A. Fiber Spinning and Drawing.- B. Characterization of the Drawn P3OT Fibers.- C. Effect of Side-Chain Length.- IV. Gels and Blends of the P3AT’s Processed from Solution.- A. Conducting Polymer Blends of Soluble Polythiophene Derivatives in Polystyrene.- B. Conducting Polymer Gels: A Self Assembling Conducting Network with Remarkably Low Percolation Threshold.- V. Electrical and Mechanical Properties of Polyaniline and Blends of Polyaniline with PPTA Processed from Solution in Sulfuric Acid.- A. Preparation of the PANI/PPTA Blends and PANI/PPTA Fiber Spinning.- B. Properties of the PANI/PPTA Fibers.- VI. Electrical and Mechanical Properties of PTV and PDMPV.- A. Preparation of Precursor Polymers, Fiber Spinning, Drawing and Conversion of PTV and PDMPV.- B. Electrical and Mechanical Properties of PTV.- C. Electrical and Mechanical Properties of PDMPV.- VII. Mechanical and Electrical Properties of Polyacetylene Films Oriented by Tensile Drawing.- A. Polymerization and Tensile Drawing.- B. X-Ray Diffraction.- C. Mechanical Properties.- D. Electrical Conductivity.- VIII. Correlation between Electrical Conductivity and Mechanical Properties.- IX. Conclusion.- Acknowledgement.- References.- The Polyanilines: Model Systems for Diverse Electronic Phenomena.- 1. Introduction.- 2. Leucoemeraldine Base (LEB).- 3. Ring Rotation Polarons and Solitons.- 4. Emeraldine Base.- 5. Pernigraniline Base.- 6. “Metallic” Polyaniline.- 7. Effects of Derivitization.- 8. Summary.- 9. Acknowledgement.- 10. References.- Structural Characterization of Conjugated Polymer Solutions in the Undoped and Doped State.- 1. Introduction.- 2. Polymer Solutions.- 2.1 Models for Single Chains.- 2.1.1 Ideal Chain.- 2.1.2 Real Chain in Good Solvent.- 2.1.3 Chain with Local Stiffness: Kratky-Porod-Model.- 2.2 Notion of Theta and Good Solvent for Linear Saturated Polymer.- 2.2.1 Mean Field Picture.- 2.2.2 Osmotic Pressure.- References.- 3. Structural Studies with Small Angle Scattering.- 3.1 Basic Principles.- 3.2 Scattering at Small Angle.- 3.3 Small Angle Scattering from Polymers in Solution.- 3.3.1 Incompressibility and Contrast Factor.- 3.3.2 Form Factor.- 3.4 Models for Polymer Chains.- 3.4.1 Ideal Chains.- 3.4.2 Chain in Good Solvent, Flexible Chain with Interactions.- 3.4.3 Scattering Function of Chain with Persistence Length.- 3.5 Scattering Measurements in Real Polymer/Solvent Systems.- 3.5.1 Polydispersity Effect.- 3.5.2 Models for Chain Cross Section.- References.- 4. Soluble Conjugated Polymers.- 4.1 Conjugated Polymers with Substituents.- 4.1.1 Substituted Polyacetylenes.- 4.1.2 Poly-n-alkylthiophenes.- 4.1.3 Polydiacetylenes.- 4.2 Diblock Copolymers and Graft Copolymers.- 4.2.1 Graft Copolymer.- 4.2.2 Sequence of Block-Copolymer.- References.- 5. Polydiacetylenes.- 5.1 Introduction.- 5.2 Statistical Conformation in Good Solvent: Yellow Solution.- 5.3 Origin of. the Blue and Red Shifts in Good Solvent: Chain Conformation and Solvatochromism.- 5.4 Color Transition: Aggregation versus Single Chain Process.- References.- 6. Study of Dopable Polymers: PANI and Poly-n-Alkylthiophenes.- 6.1 Doped Polymers in the Solid Phase.- 6.2 Doped Polymers in Solution: Poly-n-Alkylthiophene.- 6.2.1 Structure of Poly-3-butylthiophene in the Neutral State.- 6.2.2 Charged Poly-n-alkylthiophene in Solution.- References.- 7. Does Conjugated Polymer Behave Like Saturated One.- 7.1 Conformation of Soluble Conjugated Polymers: Origin of the Local Rigidity.- 7.1.1 Thermal behavior of the PDA PTS12 in Good Solvent.- 7.1.2 Experimental Evidence of the Influence of the Side-Group Extension.- 7.2 Aggregation Process for Conjugated Polymers.- 7.2.1 Observed Conformations for Polymers in Good Solvent.- 7.2.2 Model for Conjugated Polymers.- Acknowledgement.- References.- Processable Conducting Poly(3-Alkylthiopenes).- 1. Introduction.- 2. Synthesis.- 2.1 Monomer Synthesis.- 2.2 Polymerization.- 3. Characterization.- 3.1 Infrared Spectroscopy.- 3.2 NMR.- 3.3 Elemental Analysis.- 3.4 Thermal Analysis.- 3.5 Molecular Weight.- 3.6 Optical Spectra.- 3.7 X-Ray Diffraction.- 4. Processability-polymer Blends.- 4.1 Processability.- 4.2 Polymer Blends.- 5. Electronic Structure and Conformational Excitations.- 5.1 Electronic Structure.- 5.2 Conformational Excitations: Thermochromism and Solvatochromism.- 6. Doping and Stability.- 6.1 Methods of Doping.- 6.2 Conductivity.- 6.3 Dedoping.- 7. Transport Properties.- 7.1 Field Effect Transistors for Transport Property Studies.- 7.2 Poly(3-Alkylthiophene) Blends.- 8. Stretch Orientation of Poly(3-Alkylthiophenes).- 9. Applications.- 9.1 Applications through Processability.- 9.2 Electronic Devices: Transistors and Diodes.- 9.3 Nonlinear Optical Properties.- 10. Conclusions.- Acknowledgements.- References.- Controlled Molecular Assemblies of Electrically Conductive Polymers.- 1. Introduction.- 2. Fabrication of Monolayer and Multilayer Thin Films of Electrically Conductive Polymers.- 3. Molecular and Supermolecular Organizations of LB Films Containing Conducting Polymers.- 3.1 X-Ray Diffraction Studies.- 3.2 Orientation Studies by FTIR.- 3.2.1 Orientation Studies of LB Films Fabricated with the Poly(3-alkylthiophenes).- 3.2.2 Orientation Studies of LB Films Fabricated with Surface Active Pyrroles and Polypyrrole.- 3.3 Orientation Studies by NEXAFS.- 4. Electrical Properties of LB Films Containing Conducting Polymers.- 4.1 In-Plane and Transverse Conductivities.- 4.2 Dielectric Properties.- 4.3 Evaluation of Electroactive LB Films as Active Components of Thin Film Devices.- 5. Conclusions.- 6. Acknowledgements.- 7. References.- Electronic Properties of Linear Polyenes.- 1. Introduction.- 2. Terms and Concepts.- 2.1 Electronic States.- 2.2 Vibronic Spectra.- 3. Overview of Polyene Singlet States.- 4. Interpretative Model.- 5. The Ground State S0 (l1Ag).- 5.1 Geometry.- 5.2 Vibrational Frequencies.- 6. The Lowest Energy Excited Singlet State S1 (21Ag).- 6.1 Representative Spectra.- 6.2 S, Excitation Energies.- 6.2.1 Conformational Dependence.- 6.2.2 Dependence on Local Polarizability.- 6.3 S1 Vibronic Development.- 6.4 S1 Dynamical Behavior.- 7. The Strongly Allowed Excited Singlet State S2 (11Bu).- 7.1 Representative Spectra.- 7.2 S2 Excitation Energies.- 7.2.1 Conformation Dependence.- 7.2.2 Dependence on Local Polarizability.- 7.3 S2 Vibronic Development.- 7.4 Relaxation Energy.- 7.5 S0-S2 Transition Dipoles.- 8. Concluding Remarks.- 9. Acknowledgement.- 10. References.- Vibrational Spectroscopy of Polyconjugated Aromatic Materials with Electrical and Non Linear Optical Properties - A Guided Tour.- 1. Introduction.- 2. Spectroscopy vs. Material Science.- 3. Spectroscopic Observables.- 3.1 Vibrational Frequencies.- 3.2 Infrared Absorption Intensities.- 3.3 The Raman Spectra.- 4. The Vibrational Force Field. Classical vs. Quantum Mechanical Calculations.- 5. Spectroscopic Characteristics Peculiar to Poly-conjugated Materials.- 5.1 Materials in the Pristine (Insulating) State.- 5.2 Materials in the Doped (Electrically Conducting) State.- 5.3 Materials in the Photoexcited State.- 6. Theoretical Aspects of the Vibrational Spectra of Poly-conjugated Molecules.- 7. Worked-Out Study Cases.- 8. Polypyrrole.- 8.1 Structure, Symmetry and ECC Theory.- 8.2 Calculations and Comparison with the Experiments.- 8.3 Raman Spectrum of Doped PPy.- 8.4 Characterisation of PPy.- 9. Polythiophene.- 9.1 Experimental Data.- 9.2 The Structure of PTh and of its Oligomers.- 9.3 Vibrational Analysis.- 9.4 Structural Characterisation of PTh.- 10. Polyalkylthiophenes.- 10.1 Structure, Group Theory and Spectroscopic Predictions.- 10.1.1 Perfect Planar Structure.- 10.1.2 Conformationally Distorted Structure.- 10.2 EEC Theory.- 10.3 Spectroscopy and Structure of Polyalkyl-Thiophenes.- 10.4 Conformation of the Alkyl Chains.- 10.5 Structure and Thermal Behaviour of Polyalkylthiophenes.- 11. Polyparaphenylene Vinylene.- 11.1 Spectroscopic Data.- 11.2 Structure and Group Theory.- 11.3 Effective Conjugation Length and Molecular Chain Length from Optical Data.- 11.4 Group Theory and ECC Theory.- 11.5 Structure of PPV from Spectroscopy.- 12. Conclusions.- Acknowledgement.- References.- Third Order Nonlinear Optical Effects in Conjugated Polymers.- 1. Introduction.- 1.1 Nonlinear Pplarization.- 1.2 Origin of Second Order Hyperpolarizability.- 1.3 Coherent Nonlinearities.- 1.4 Second Order Hyperpolarizability of Centro-symmetric and Non-Centrosymmetric Molecules. Influence of Polymer Length.- 1.4.1 Centrosymmetric Molecules.- 1.4.2 Non-Centrosymmetric Molecules.- 1.5 Conformational Effects.- 2. Thin Film Preparation Methods.- 2.1 Langmuir-Blodgett Technique.- 2.2 Solution Casting.- 2.3 Vacuum Evaporation-Epitaxy.- 3. Principal x(3) Characterization Techniques.- 3.1 Third Harmonic Generation.- 3.1.1 Third Harmonic Generation in Nonabsorbing Stratified Media.- 3.1.2 Harmonic Generation in Absorbing Media.- 3.1.3 Multiple Reflections.- 3.1.4 Harmonic Generation in Focused Laser Beams.- 3.2 Third Harmonic Generation in Thin Films and in Solutions.- 3.2.1 Thin Film Case.- 3.2.2 THG in Polymer Solutions.- 3.3 Electric Field Induced Second Harmonic Generation.- 3.3.1 Thin Film Case.- 3.3.2 Centrosymmetric Molecules in Solution.- 3.3.3 Non-Centrosymmetric Molecules in Solution.- 3.4 Four Wave Mixing Experiments.- 3.5 Optical and Quadratic Kerr Effect.- 3.6 Optical Stark Effect.- 3.7 Saturation Absorption.- 3.8 Photoinduced Absorption.- 4. Frequency Spectrum and Resonance Effects in x(3).- 4.1 Frequency Variation of x(3): Modelisation.- 4.2 Determination of µ01.- 4.3 Frequency Variation of x(3) (-3?;?,?,?) and x(3) (-2?;?,?,O).- 5. Multiphoton Resonances.- 6. Nonlinear Optical Dichroism.- 7. Perspectives of Applications.- 7.1 Frequency Conversion.- 7.2 Optical Switching and Directional Couplers.- 7.3 Optical Bistability.- References.- The Semiconductor Device Physics of Polyacetylene.- 1. Introduction.- 2. Electronic Excitations in Conjugated Polymers.- 3. Polymer Processing and Device Fabrication.- 3.1 The Durham Precursor Route to Polyacetylene.- 3.2 Device Fabrication.- 4. Electronic Properties of Durham-Route Polyacetylene.- 4.1 Electronic Structure.- 4.2 Electronic Transport.- 4.3 Electromodulation of Optical Absorption.- 5. Schottky Barrier Diodes.- 5.1 The Schottky Barrier.- 5.2 Electrical Characteristics.- 5.3 Electro-Optic Properties.- 5.4 Electronic States in the Polyacetylene Schottky Barrier.- 6. MIS Structures.- 6.1 The Field-Effect Device.- 6.2 Electrical Characterisation of MIS Structures.- 6.2.1 Silicon Dioxide as Insulator.- 6.2.2 Polymer Insulator Layers.- 6.3 Electro-Optical Properties of the MIS Structure.- 6.3.1 Electronic Excitations of Solitons.- 6.3.2 Vibrational Excitations of Solitons.- 6.4 Modelling of Electronic Structure in the Accumulation Layer.- 7. MISFET Devices.- 7.1 Fabrication.- 7.2 Poly n-Silicon Source and Drain Contacts.- 7.3 Charge Transport in Polyacetylene.- 8. General Discussion.- Acknowledgements.- References.