Combining logical gates and organizing them into specific executable sequences serves as the basis for programming electronic devices. For materials the programming is achieved by combining specific sequentially positioned chemical and/or physical motifs to achieve desirable functions. The most obvious programmable systems are the strands of DNA and RNA that serve as the huge and accurate information database with even more complex tools containing instructions for accurate regulation, replication and translation of encoded information.

In recent years there have been tremendous efforts put into developing synthetic programmable materials. Fewer efforts have been made to understand molecular processes leading to stimuli-responsive behavior. Until the turn of the 21st century only very few research articles considered the term ‘stimuli responsiveness’ in the context of materials science, chemistry, physics or engineering. This vocabulary was rarely part of symposia or scientific meetings. At that time, most would view polymers and other materials as functional. Plastics, remember son, the future is in plastics, the famous phrase from The Graduate movie with Dustin Hoffman, said it all. Indeed, polymers serve admirable functions, ranging from paints that protect substrates, or protective armor saving the lives of soldiers, or space industries, not to mention artificial organs, simple catheters or pacemakers, or even cosmetics. You name the field, polymers are there. Since 2002, when the National Science Foundation founded the first Materials Research Science Engineering Center (MRSEC) on Stimuli Responsive Polymeric Films and Coatings, many new research activities have emerged and continue, as does the amazing and headline-making new wave of ideas and discoveries, as well as technological opportunities. Today, many researchers around the world are actively involved in searching for new materials with stimuli-responsive characteristics.

In the last decade at least 30 books have been edited and encompass a variety of topics related to stimuli responsiveness. So why write another one? While exciting findings detailing individual research activities can be found in many excellent review articles and edited monographs, the field is mature enough that new principles of design, synthesis and characterization have been established. Thus, for newcomers entering the field, as well as for those who are already immersed in it, this book will hopefully serve as a stimulating source of new knowledge and resourceful information for further advances. Senior undergraduate and graduate students, majoring in materials chemistry and materials science and engineering, as well as chemistry and physics, tested the content of the book. The content appeared to be attractive and this modern core course offered at Clemson University attracted the curiosity of new generations of scientists, yet offered modern views of the new ideas and technologies. This is reflected in the book content, which covers a broad range of topics, from controlled polymer synthesis to physicochemical aspects of stimuli responsiveness in nanomaterials, brushes, surfaces and interfaces, photonic and photochromic materials, field and bioresponsive materials as well as self-healing. As stimuli responsiveness typically requires an input, as a trigger to execute the instructions and perform desired functions, in many cases the output is required to end a given event.

Mother Nature is probably the best teacher and inspiration for stimuli responsiveness. Biological systems exhibit an extraordinary ability to heal wounds autonomously; for plants to heal mechanical damage, where different substances such as suberin, tannins and phenols are activated to prevent further lesions. Similarly, mechanical damage to human skin resulting in the outward flow of blood cells is arrested by the crosslinked network of fibrin, leading to self-repair. One common feature in these bio-events is the presence of heterogeneous, often multi-layered morphologies that interact with each other and respond to external or internal stimuli. These intriguing features stimulated the formation of this new and exciting field of science. Although the field is particularly close to polymer scientists because of inherent similarities of biological systems, other materials are not far behind. Almost any heterogeneous material may exhibit stimuli responsiveness, as long as interfacial regions can facilitate molecular responses and rearrangements. Polymers, due to their versatile features, exhibit a great degree of flexibility, and designing them from molecular blocks to form manufactured architectures at nano, micro, macro and larger scales is critical for creating stimuli-responsive materials capable of autonomous functions. This is reflected in the first introductory chapter, which uses the human eye as an example to delineate the complexity of challenges. The remaining parts of the introduction define general concepts that will be interwoven throughout the book. The remaining chapters are divided into synthetic aspects of stimuli-responsive materials, whereas the remaining chapters feature the development of novel stimuli-responsive materials with the ability of signaling, reorganization, sensing and self-repair at various length scales. In essence, the main objective of this book is the programmable design of materials that can retain a set of specifically coded instructions by virtue of a chemical structure in an effort to be able to perform desired functions on demand. Because these materials hold great promise in a variety of applications, understanding the fundamental concepts that govern stimuli-responsive behavior is critical; how chemical information can be translated into function is still to be understood. Considering the fact that so many excellent publications and ideas have been published in the last decade, the author apologizes that not all could be incorporated, and only selected examples could be used.

This book went through several tests, exams, and iterations. As in every effort of this nature, it could not be completed without the tremendous help of the end users, the students and postdocs. I am grateful to all Clemson University students who used the content of this book and provided useful insights in various capacities. All Urban Research Group members, past and present (www.clemson.edu/ces/urbanresearch/), who have taught me a lot over the years, and allowed me to be their scientific mentor and research advisor. I am particularly thankful to my current group members, Ying Yang, Chris Chornat, Dmitriy Davidovich, Chunling Lu, Tugba Demir, Laura Smith, Yanting Xing, Hiroyuki Mitsunaga and Zhanhua Wang, whose efforts are particularly appreciated. The author is also thankful to his family, Kasia, Ania and Mike, without whom this book could not have developed.

Marek W. Urban

Clemson University