This book describes the relaxation dynamics of rubbery materials, with the objective of providing a molecular basis for many physical properties. As the term comprises any amorphous, flexible macromolecule above its glass-transition temperature, rubber includes a broad class of substances, with a richness of behavior rivaled by few materials. The focus is mainly on the phenomenology, emphasizing anomalies and aspects that are incompletely understood and thus productive avenues for future research. Rubber is especially interesting because it has unique properties. It can exist in a state of equ ... More

This book describes the relaxation dynamics of rubbery materials, with the objective of providing a molecular basis for many physical properties. As the term comprises any amorphous, flexible macromolecule above its glass-transition temperature, rubber includes a broad class of substances, with a richness of behavior rivaled by few materials. The focus is mainly on the phenomenology, emphasizing anomalies and aspects that are incompletely understood and thus productive avenues for future research. Rubber is especially interesting because it has unique properties. It can exist in a state of equilibrium, unlike glassy or semicrystalline plastics, thermosetting resins, fibers, etc. These polymers have path-dependent morphologies and process-specific properties, which frustrate scientific inquiry, notwithstanding their practical utility. Among all materials only rubber exhibits high elasticity—the ability to recover from very large deformations. This property underlies most applications of elastomers and gave rise to its own field of study. Despite these singular characteristics, rubber is arguably the prototype for relaxation in soft matter. By copolymerizing different monomers, an enormous variety of chemical structures are available that, along with the ease of avoiding crystallization, makes make rubber ideal for the study of the glass transition, a major unsolved problem in condensed-matter physics. In the glassy state or when vitrification is imminent, polymers cannot easily be distinguished from molecular liquids, and the correspondence of many phenomena makes distinctions between molecular and polymeric liquids artificial. Accordingly, the scope of this book is not limited to polymer science, with the discussion often extending to small-molecule compounds, including simple liquids and liquid crystals.