Soft Matter Gradient Surfaces: Methods and Applications

Book Preface

Although it was first introduced by the French physicist Madeleine Veyssi´e around 1970, the term soft matter caught true attention only after Pierre-Gilles de Gennes used it in his Nobel speech in 1991. Soft matter represents a very rapidly developing subset of structures generally called condensed matter. It encompasses both naturally occurring structures (i.e., biomolecules) and synthetic substances (i.e., liquids, liquid crystals, colloids, membranes, gels, foams, and many subsets thereof).

These structures range in size from a single chemical repeat unit to molecular clusters to large macromolecules made up of thousands of repeat units. One feature that distinguishes soft materials from hard condensed matter is that the former can be deformed readily by applying some external force (i.e., mechanical, electrical, or magnetic). Governed by short and long range interactions, the individual soft matter building blocks can organize into well-ordered structures, spanning nanoscopic (molecular) to mesoscopic (cluster-like) length scales. Although in most instances, the organization takes place spontaneously via self-assembly driven primarily by van der Waals interactions, additional fine tuning can be achieved by applying an external field or by forcing the self-assembly to take place in the confined spaces of various geometries. Nowadays, the field of soft materials represents an exciting meeting arena for chemists, physicists, biologists, and engineers who design, build, and probe the characteristics of both the individual blocks and larger assemblies made up of those blocks.

Self-assembly of soft materials at or near interfaces or surfaces offers additional benefits in that (i) it provides control over system dynamics, that is, depending on the system setup, the building blocks can be either completely mobile or immobilized temporarily or permanently; (ii) novel self-assembly motifs can be generated that are not necessarily obtainable in bulk; and (iii) the spatial distribution of the assembly patterns can be adjusted by depositing the individual building blocks onto substrates of various geometries and chemistries. The characteristics of the discrete building blocks as well as their spatial arrangement, in turn, endow such structures with unprecedented properties and functionalities. Numerous publications have reported on the interfacial assembly of soft materials and the advantages they provide in controlling functionality of surfaces, and studying important physico-chemical phenomena by means of sophisticated analytical methods and tools.