Introductions to solid state physics have, ever since the initial book by F. Seitz in 1940, concentrated on simple crystals, with few atoms per cell, bonded together by strong ionic, covalent, or metallic bonds. References to weaker bonds, such as van der Waals forces in rare gases, or to geometric or chemical disorder (e.g., alloys or glasses) have been limited. The physical understanding of this ?eld started well before Seitz’s book and led to a number of Nobel prizes after the last war. Applications cover classical metallurgy, el- tronics, geology and building materials, as well as electrical and ionic transport, chemical reactivity, ferroelectricity and magnetism. But in parallel with this general and well publicized trend, and sometimes earlier as far as physical concepts were concerned, an exploration and increasingly systematic study of softer matter has developed through the twentieth century. More often in the hands of physical chemists and crystallographers than those of pure physicists, the ?eld had for a long time a reputation of complexity. If progress in polymers was steady but slow, interest in liquid crystals had lain dormant for forty years, after a bright start lasting through 1925, to be revived in the late 1960s based on their possible use in imaging techniques. The optoelectronic properties of the ?eld in general are even more recent.

Many materials have complex structural and dynamic properties intermediate between those of crystals and fluids. Among these are liquid crystals, with their well-known orientational order; colloids; polymer solutions and melts; foams; and gels; collectively these have come to be called "soft matter." These materials generally consist of organic molecules that interact weakly; as a result, thermal fluctuations, external fields, and boundary effects strongly influence their structure and properties. This sensitivity raises interesting new problems in basic physics, chemistry, and materials science; offers a path of thinking about some processes in biological systems; and opens numerous possibilities for technological applications. This textbook for graduate students in physics or chemical physics begins with a discussion of chemical bonds, interactions between particles, and the resulting molecular arrangements. The concept of order parameter leads to a discussion of phase transitions, elasticity and dynamics, followed by a review of fractals and growth phenomena. A significant portion of the book deals with defects of topological nature that accompany various types of order. The book concludes with chapters on surface phenomena, stability of colloidal systems, and structural properties of polymers. The detailed exposition, the emphasis on physical principles, and the exercises at the end of each chapter will make this book a valuable introduction for graduate students and researchers to this rapidly growing field.