Self–Healing Polymers: From Principles to Applications

Self–healing is a well–known phenomenon in nature: a broken bone merges after some time and if skin is damaged, the wound will stop bleeding and heals again. This concept can be mimicked in order to create polymeric materials with the ability to regenerate after they have suffered degradation or wear. Already realized applications are used in aerospace engineering, and current research in this fascinating field shows how different self–healing mechanisms proven successful by nature can be adapted to produce even more versatile materials. The book combines the knowledge of an international panel of experts in the field and provides the reader with chemical and physical concepts for self–healing polymers, including aspects of biomimetic processes of healing in nature. It shows how to design self–healing polymers and explains the dynamics in these systems. Different self–healing concepts such as encapsulated systems and supramolecular systems are detailed. Chapters on analysis and friction detection in self–healing polymers and on applications round off the book.

List of Contributors XIII Introduction 1 Wolfgang Binder Part One Design of Self–Healing Materials 5 1 Principles of Self–Healing Polymers 7 Diana Döhler, Philipp Michael, and Wolfgang Binder 1.1 Introductory Remarks 7 1.2 General Concept for the Design and Classifi cation of Self–Healing Materials 8 1.3 Physical Principles of Self–Healing 11 1.4 Chemical Principles of Self–Healing 15 1.5 Multiple versus One–Time Self–Healing 49 1.6 Resume and Outlook 53 Acknowledgments 53 References 53 2 Self–Healing in Plants as Bio–Inspiration for Self–Repairing Polymers 61 Thomas Speck, Rolf Mülhaupt, and Olga Speck 2.1 Self–Sealing and Self–Healing in Plants: A Short Overview 62 2.2 Selected Self–Sealing and Self–Healing Processes in Plants as Role Models for Bio–Inspired Materials with Self–Repairing Properties 63 2.3 Bio–Inspired Approaches for the Development of Self–Repairing Materials and Structures 75 2.4 Bio–Inspired Self–Healing Materials: Outlook 85 Acknowledgments 85 References 86 3 Modeling Self–Healing Processes in Polymers: From Nanogels to Nanoparticle–Filled Microcapsules 91 German V. Kolmakov, Isaac G. Salib, and Anna C. Balazs 3.1 Introduction 91 3.2 Designing Self–Healing Dual Cross–Linked Nanogel Networks 92 3.3 Designing “Artifi cial Leukocytes” That Help Heal Damaged Surfaces via the Targeted Delivery of Nanoparticles to Cracks 101 3.4 Conclusions 110 References 111 Part Two Polymer Dynamics 113 4 Structure and Dynamics of Polymer Chains 115 Ana Rita Brás, Wim Pyckhout–Hintzen, Andreas Wischnewski, and Dieter Richter 4.1 Foreword 115 4.2 Techniques 116 4.3 Structure 117 4.4 Dynamics 120 4.5 Application to Self–Healing 130 4.6 Conclusions and Outlook 133 References 135 5 Physical Chemistry of Cross–Linking Processes in Self–Healing Materials 139 Joerg Kressler and Hans–Werner Kammer 5.1 Introduction 139 5.2 Thermodynamics of Gelation 141 5.3 Viscoelastic Properties of the Sol–Gel Transition 143 5.4 Phase Separation and Gelation 147 5.5 Conclusions 150 References 150 6 Thermally Remendable Polymers 153 Tom Engel and Guido Kickelbick 6.1 Principles of Thermal Healing 153 6.2 Inorganic–Organic Systems 164 6.3 Efficiency, Assessment of Healing Performance 165 6.4 Conclusions 168 Acknowledgments 169 References 169 7 Photochemically Remendable Polymers 173 Jun Ling, Ming Qiu Zhang, and Min Zhi Rong 7.1 Background 173 7.2 Molecular Design 178 7.3 Reversible Photo–Crosslinking Behaviors 182 7.4 Evaluation of Photo–Remendability 185 7.5 Concluding Remarks 188 Acknowledgments 189 References 189 8 Mechanophores for Self–Healing Applications 193 Charles E. Diesendruck and Jeffrey S. Moore 8.1 Introduction 193 8.2 Mechanochemical Damage 194 8.3 Activation of Mechanophores 198 8.4 Mechanochemical Self–Healing Strategies 202 8.5 Conclusions and Outlook 210 References 211 9 Chemistry of Crosslinking Processes for Self–Healing Polymers 215 Roberto F.A. Teixeira, Xander K.D. Hillewaere, Stijn Billiet, and Filip E. Du Prez 9.1 Introduction 215 9.2 Extrinsic Self–Healing Materials 215 9.3 Intrinsic Self–Healing Materials 229 9.4 Concluding Remarks and Future Outlook 237 References 238 10 Preparation of Nanocapsules and Core–Shell Nanofi bers for Extrinsic Self–Healing Materials 247 Daniel Crespy and Yi Zhao 10.1 Selected Preparation Methods for the Encapsulation of Self–Healing Agents 247 10.2 Mechanically Induced Self–Healing 251 10.3 Stimuli–Responsive Self–Healing Materials 258 10.4 Novel Approaches and Perspectives 264 Abbreviations 265 References 266 Part Three Supramolecular Systems 273 11 Self–Healing Polymers via Supramolecular, Hydrogen–Bonded Networks 275 Florian Herbst and Wolfgang H. Binder 11.1 Introduction 275 11.2 Dynamics of Hydrogen Bonds in Solution 279 11.3 Supramolecular Gels 280 11.4 Self–Healing Bulk Materials 284 11.5 Conclusions 297 Acknowledgment 297 References 298 12 Metal–Complex–Based Self–Healing Polymers 301 Stefan Bode, Benedict Sandmann, Martin D. Hager, and Ulrich S. Schubert 12.1 Stimuli–Responsive Metallopolymers 305 12.2 Self–Healing Metallopolymers 307 12.3 Summary and Outlook 310 Acknowledgments 311 References 311 13 Self–Healing Ionomers 315 Nico Hohlbein, Max von Tapavicza, Anke Nellesen, and Annette M. Schmidt 13.1 Introduction 315 13.2 Basic Principles of Ionomers 315 13.3 Ionomers in Self–Healing Systems 322 13.4 Actual Developments and Future Trends in Ionomeric and Related Self–Healing Systems 327 References 331 Part Four Analysis and Friction Detection in Self–Healing Polymers: Macroscopic, Microscopic and Nanoscopic Techniques 335 14 Methods to Monitor and Quantify (Self–) Healing in Polymers and Polymer Systems 337 Ranjita K. Bose, Ugo Lafont, Jesús M. Vega, Santiago J. Garcia, and Sybrand van der Zwaag 14.1 Introduction 337 14.2 Visualization Techniques 338 14.3 Healing of Mechanical Properties 343 14.4 Healing of Functional Integrity 347 14.5 Summary 356 References 356 15 Self–Healing Epoxies and Their Composites 361 Henghua Jin, Kevin R. Hart, Anthony M. Coppola, Ryan C. Gergely, Jeffrey S. Moore, Nancy R. Sottos, and Scott R. White 15.1 Introduction 361 15.2 Capsule–Based Healing System 362 15.3 Vascular–Based Healing Systems 368 15.4 Intrinsic Healing Systems 371 15.5 Conclusions 375 References 376 16 Self–Healing Coatings 381 Dmitry G. Shchukin, Dimitriya Borisova, and Helmuth Möhwald 16.1 Introduction into Self–Healing Coatings 381 16.2 Concept of Micro– and Nanocontainer–Based Self–Healing Coatings 382 16.3 Types of Nanocontainers 386 16.4 Characterization of Nanocontainer–Based Self–Healing Coatings 389 16.5 Conclusions and Current Trends 395 References 396 17 Application of Self–Healing Materials in Aerospace Engineering 401 Liberata Guadagno, Marialuigia Raimondo, Carlo Naddeo, and Pasquale Longo 17.1 General Considerations 401 17.2 Conclusions 410 References 411 Index 413

Wolfgang H. Binder is Professor for Macromolecular Chemistry at the University of Halle, Germany. He received his PhD in Organic Chemistry in 1995 at the University of Vienna. In his post doc research at Emory University, USA, he specialized on colloidal chemistry/macromolecular chemistry. In 1997 he became an Assistant Professor at the Technical University of Vienna and in 2004 Associate Professor. His research is focused on tailored synthetic methods (living polymerization methods) and analytical polymer science, with applications in material science, nanotechnology and medicine; Wolfgang H. Binder has published over 120 scientific articles.