Dielectric Properties of Ionic Liquids (eBook)

Marian Paluch studied physics at the University of Silesia in Katowice. In 1998 he gained his Ph.D. with a study on the effect of pressure on the molecular dynamics of glass-forming liquids. In 2004 he completed his habilitation at the University of Silesia and became professor in 2010. He spent two years at the Max Planck Institute for Polymer Research in Mainz in the group of Prof. E. W. Fischer. Later he was appointed as a visiting scientist at the Naval Research Laboratory in Washington DC, the University of Akron, the Hebrew University, the University of Pisa and the University of Tennessee. Marian Paluch is currently the head of the Biophysics and Molecular Physics Department where he is developing high pressure techniques for studying the molecular dynamics in condensed matter, charge transport in ionic liquids, phase transitions and crystallization kinetics.

Preface 6
Contents 9
1 Introduction to Ionic Liquids 11
Abstract 11
1.1 Synthetic Ways to Ionic Liquids as Source for Possible Impurities 13
1.2 Liquid Range of Ionic Liquids 16
1.3 Viscosity of Ionic Liquids 20
1.4 Density of Ionic Liquids 24
1.5 Polarity of Ionic Liquids 24
1.6 New Polymer Materials Derived from Ionic Liquids 27
References 29
2 Rotational and Translational Diffusion in Ionic Liquids 38
Abstract 38
2.1 Introduction 39
2.2 Experimental Details 41
2.3 Results and Discussion 41
2.3.1 Charge Transport and Dynamic Glass Transition in Ionic Liquids 42
2.3.2 Elucidating the Correlation Between Characteristic Hopping Lengths and Molecular Volumes of Ionic Liquids 53
2.4 Conclusions 57
Acknowledgments 57
References 57
3 Femto- to Nanosecond Dynamics in Ionic Liquids: From Single Molecules to Collective Motions 61
Abstract 61
3.1 Introduction 62
3.2 Broadband Dielectric Spectra of Ionic Liquids 63
3.3 Translation or Rotation—Comparison to Computational Results 66
3.4 Local Versus Global Dielectric Response—Comparison to Solvation Response 68
3.5 Balanced Sensitivities—Comparison to Optical Kerr Effect Spectroscopy 69
3.6 Adding Molecular Specificity—Comparison to Ultrafast Infrared Spectroscopy 71
3.7 Conclusions 73
Acknowledgments 74
References 75
4 High-Pressure Dielectric Spectroscopy for Studying the Charge Transfer in Ionic Liquids and Solids 80
Abstract 80
4.1 Conductivity Measurements Under High-Pressure Conditions. How to Exert Pressure on the Sample? 81
4.2 Pressure Sensitivity of Ion Dynamics. How Much Pressure Do We Need to “Supercool” Ionic System? 84
4.3 Thermal and Density Fluctuations to the Temperature Dependence of ?dc at Ambient and Elevated Pressure 94
4.4 Density Scaling of Ionic Systems 98
4.5 Relation Between Ion Dynamics and Structural Relaxation at Ambient and Elevated Pressure 103
4.5.1 Are the Stockes–Einstein and Walden Laws Always Satisfied? 103
4.5.2 How to Quantify Decoupling Between the Charge Transfer and Structural/Segmental Relaxation in Ionic Conductors? 110
4.5.3 How to Control the Time Scale Separation Between Charge and Mass Diffusion? 113
4.6 Conclusions and Perspectives 116
Acknowledgement 117
References 118
5 Glassy Dynamics and Charge Transport in Polymeric Ionic Liquids 121
Abstract 121
5.1 Introduction 121
5.2 Experimental Details 122
5.3 Results and Discussion 123
5.4 Conclusion 132
Acknowledgments 132
References 132
6 Ionic Transport and Dielectric Relaxation in Polymer Electrolytes 136
Abstract 136
6.1 Introduction 136
6.2 Dielectric Relaxation in Polymer Electrolytes 137
6.2.1 Analysis of Dielectric Spectra of Polymer Electrolytes 137
6.2.1.1 Spectrum Analysis Protocols 138
6.2.1.2 Analysis of Electrode Polarization: Ion Number Density and Diffusivity 140
6.2.2 Low Salt Concentration: Emergence of Ionic Mode 143
6.2.2.1 Pressure Dependence of the Ionic Mode 145
6.2.2.2 Slow Segmental Relaxation 146
6.2.2.3 Nature of the Ionic Mode 146
6.2.3 Emergence of Additional Relaxation Modes at Higher Salt Concentrations 148
6.3 Ionic Transport in Polymer Electrolytes 150
6.3.1 Theory of Ionic Mobility in Electrolyte Solutions 150
6.3.2 Models of Ionic Transport in Polymer Electrolytes 151
6.3.2.1 Free-Volume Model 151
6.3.2.2 Dynamic Bond Percolation Model 153
6.3.3 Coupling and Decoupling Between Conductivity and Polymer Relaxation 154
6.3.3.1 Observation of Decoupling in Polymer Electrolytes 154
6.3.3.2 Walden Plot Analysis 157
6.4 Summary 159
Acknowledgments 159
References 159
7 Electrochemical Double Layers in Ionic Liquids Investigated by Broadband Impedance Spectroscopy and Other Complementary Experimental Techniques 162
Abstract 162
7.1 Broadband Impedance Spectroscopy 163
7.1.1 Introduction 163
7.1.2 Theory of Impedance Spectroscopy 164
7.1.3 Practical EIS Pitfalls 166
7.1.3.1 Cell Design for Three-Electrode Measurements 167
7.1.3.2 Non-stationary Electrochemical Systems 167
7.1.3.3 Fitting Algorithms 167
7.1.4 Application to Metal | IL Interfaces 168
7.1.4.1 Introduction 168
7.1.4.2 [Pyrr1,4]FAP 170
7.1.4.3 [EMIm]FAP 171
7.1.4.4 Conclusion 171
7.2 Scanning Tunneling Microscopy 172
7.2.1 Introduction 172
7.2.2 Application to Metal | IL Interfaces 174
7.3 X-Ray Reflectivity 176
7.3.1 Introduction 176
7.3.2 Application to Solid | IL Interfaces 177
7.4 Atomic Force Microscopy 179
7.4.1 Introduction 179
7.4.2 AFM for the Investigation of Solid | IL Interfaces 181
7.5 Surface Force Apparatus 185
7.5.1 Introduction 185
7.5.2 SFA Studies of Solid | IL Interfaces 187
7.6 Surface-Enhanced Raman Spectroscopy (SERS) and Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) 190
7.7 Sum-Frequency Generation (SFG) Vibrational Spectroscopy 192
References 193
8 Dielectric Properties of Ionic Liquids at Metal Interfaces: Electrode Polarization, Characteristic Frequencies, Scaling Laws 198
Abstract 198
8.1 Introduction 198
8.2 Materials and Methods 199
8.2.1 Materials 199
8.2.2 Methods 200
8.3 Dielectric Properties of Ionic Liquids: Characteristic Frequencies and Universal Scaling Laws 200
8.4 Electrode Polarization and Ionic Charge Transport at Metal Interfaces: Theoretical Model 205
8.4.1 Analytical Calculations 206
8.4.1.1 The Onset and the Full Development of Electrical Polarization Effects 206
8.4.1.2 The Inflection Point Fi 208
8.4.1.3 Electrode Polarization: The Asymptotic Behavior for x ? 0 209
8.4.1.4 Gradients of Local Dielectric Properties 211
8.5 The Complex Dielectric Function of Ionic Liquids in the Interfacial Layers at Metal Electrodes 212
8.6 Conclusions 216
References 217
9 Decoupling Between Structural and Conductivity Relaxation in Aprotic Ionic Liquids 218
Abstract 218
9.1 Introduction 218
9.2 Heat Capacity Spectroscopy 224
9.3 Results 227
9.3.1 [C6MIm][NTf2] 227
9.3.2 [C4MIm][NTf2] 229
9.3.3 [C8MIm][NTf2] 230
9.4 Summary 232
Acknowledgment 234
References 234
Index 239