Introduction to Soft Matter Physics

Luwei Zhou

• Publisher: WSPC
• Year: 2019
• eBook ISBN: 9789813275119
• Topic: Physical Sciences
• Subtopic: Condensed Matter

Soft matters differ from hard ones essentially due to former's relatively weak interaction which is comparable to k B T rm (T rm = room temperature) — this results in the major characteristics of soft matters such as 'strong reactions upon weak actions'.

Developed over a period of 10 years through soft matter physics lectures for both graduate and undergraduate students in Fudan University, this textbook not only concentrates on the basic interactions inside soft matters through a reductionist approach, but also introduces the exploratory works on the complexity of soft matters in methods of system science.

Other important topics in soft matter physics which are included involve static and dynamic electrorheological (ER) effects — an important 'model animal' in the subject, granular media — which explains the thermodynamics of sands and its dynamics, and the Onsager principle of least energy dissipation rate which has been adapted in this textbook to see how it governs the optimal paths of a system's deviation from and restoration to equilibrium.

The subject of soft matter physics is still in its infancy, making it highly exciting and attractive. If you like a challenging subject, you will most certainly fall in love with soft matter physics at first read!

Contents:

• Characteristics of Soft Matters
• Basic Interactions in Soft Matters
• Structures Determination of Soft Matters
• Complexity of Soft Matters
• Static Electrorheological Effect
• Dynamic of Electrorheological Effects
• Granular Systems

Readership: Students at the undergraduate to graduate level who are interested in the study of soft matter physics. Soft Matter Physics;Interaction of Soft Matter;Electrorheological Effect;Complex Fluid;Non-Newtonian Fluids;Granular Systems;Suspension;Colloid;Magnetorheological Fluid;Neutron Scattering;Neutron Diffraction;Structure of Soft Matter;Complexity of Soft Matter0 Key Features:

• Concentrates on physics mechanisms with detailed explanations of interesting applications of soft matters, such as liquid body armors, electrorheolofical effect, earthquake, sand soilization which will surely stimulate serious discussions among students
• Discusses the neutron diffraction in studying the structures of soft matters
• Expounds the complexity of soft matters, guiding students to view "complex" behaviors of soft matters in a simpler way

Chapter 1

Characteristics of Soft Matters

1.1Why Soft Matters

1.1.1Why should we study soft matter physics

French scientist Pierre-Gilles de Gennes won the Nobel Prize in Physics in 1991 “for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers” as described by the Nobel Prize committee. His Nobel Lecture was entitled Soft Matter [1.1]. The French version of soft matter, matière molle, was invented as a joke by M. Veyssié in Orsay around 1970 [1.2]. The term matière molle has a double meaning in French: both soft matter and useless or weak matter. “Soft matter” was introduced to describe something that goes plastic with soap bubbles, from gels, elastomers, liquid crystals, cosmetic creams, mud, ceramic paste, etc. Soft matters are usually called complex fluids in North America.

Soft matters refer to the soft condensed matters — the materials other than those in gas and solid states, but usually not including simple fluids. From the point of view of materials, soft matter physics is concerned with physical principles governing the behaviors of foams, liquid crystals, polymers, colloidal dispersions, micro emulsion, micelle and various types of biological liquids, suspensions, and even granular materials, because of their wide applications.

What are the major differences between “soft” and “hard” matters?

A common feature that all soft matters or complex fluids have is that they respond a lot even under a small action which is not necessarily mechanical. Soft matters are usually very sensitive to external actions, while “hard” matters are usually not sensitive to them. P.G. de Gennes likes using the example of the Indian boot to explain the essence of soft matters. Indians take the sap from the Hevea tree and smear their feet with it. After 20 minutes, under the affect of oxygen, the liquid sap, or latex, coagulates and becomes a solid boot. Oxygen was later substituted with sulfur to make a stable boot. It has been noted that only 1 in 200 carbon atoms in the latex react with a sulfur atom, and yet the sulfuration is an extremely weak chemical reaction. Nevertheless, the liquid matter becomes solid matter. A drop of friction reducer made of a kind of polymer would greatly reduce the friction of water flow in a water hose, and greatly increase the height of a water column out of a water hose. Small causes create large effects: soft matter can be transformed by weak external actions. P. G. de Gennes says “this is the central and fundamental definition of soft matter.” [1.3]

The reason why soft matters respond strongly to weak actions is that entropy plays an important role in soft matters, while in hard matters, inner energy does so. The basic characteristics of soft matters include nonlinear responses to external forces, self-organization and dilation symmetry, which can be seen in the later part of this chapter.

As pointed out by the Royal Swedish Academy of Sciences in the press release about the Nobel Prize in Physics in 1991, “P. G. de Gennes has by some judges been called ‘the Isaac Newton of our time’. The reason for this highly appreciative epithet is probably that de Gennes has succeeded in perceiving common features in order phenomena in very widely differing physical systems, and has been able to formulate rules for how such systems move from order to disorder. Some of the systems de Gennes has treated have been so complicated that few physicists had earlier thought it possible to incorporate them at all in a general physical description. Physicists often take pride in dealing with systems that are as simple and ‘pure’ as possible, but de Gennes’ work has shown that even ‘untidy’ physical systems can successfully be described in general terms. In this way he has opened new fields in physics and stimulated a great deal of theoretical and experimental work in these fields. While this is pure research, it has also meant the laying of a more solid foundation for the technical exploitation of the materials mentioned here: liquid crystals and polymers.” I. Lindgren of the Royal Swedish Academy of Sciences said in his Presentation Speech (December 10, 1991) that “the major progress in science is often made by transferring knowledge from one discipline to another. Only few people have sufficiently deep insight and sufficient overview to carry out this process. De Gennes is definitely one of them.”

Facing such honor, the reply of P.G. de Gennes was very calm: in his Nobel Lecture in 1991 he quoted “a poem from an experiment on soft matter” by Boudin from the following drawing: Have fun on sea and land/Unhappy it is to become famous/Riches, honors, false glitters of this world/All is but soap bubbles [1.1].

The aim of condensed matter physics is to understand the collective properties of large assemblies of atoms and molecules in terms of interactions between their component parts. Soft condensed matter physics concerns the study of the structure, physical properties and electronic states of soft matters. It includes also the critical behaviors of liquid, such as liquid-solid, liquid-gas and metal-nonmetal transition of liquid. Soft matter physics studies surface, interface and wetting of liquid, transportation and properties of liquid in porous media.

Why should we study soft matters? As pointed out by Prof. Feng Duan, the frontiers of physics in the 21st century are the interaction of strongly correlated electrons, microstructure of nanometer-sized materials and soft condensed matters. The wide potential applications of soft matters and the exploration of new science have become two major reasons for increasing interest in the study of soft condensed matter physics.

P. G. de Gennes pointed out [1.1] that “granular matter is a new type of condensed matter, as fundamental as a liquid or a solid and showing in fact two states: one fluid-like, one solid-like. But there is as yet no consensus on the description of these two states! Granular matter, in 1998, is at the level of solid-state physics in 1930”. It has been found that soft matter physics is a brand new area of physics, where one may find new phenomena that cannot be explained with current knowledge of physics. For instance, in Chapter 7, on granular systems, we will mention that axial segregation of granular material of different sizes in a cylinder remains unexplained.

Soft matters are complex systems, which also show many types of nonlinear effects. This is also a reason why people are interested in the study of soft matters.

1.1.2The interests of soft matter physics

The amazing aspect of any science is that it is full of unknowns. In a young discipline such as soft condensed matter physics, unknowns as well as unsolved problems occupy the majority of the subject.

(1)Nature of glasses and the glass transition

Glass is an amorphous solid that exhibits a glass...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Dedication
• Preface
• List of Tables
• List of Figures
• Chapter 1 Characteristics of Soft Matters
• Chapter 2 Basic Interactions in Soft Matters
• Chapter 3 Structure Determination of Soft Matters
• Chapter 4 Complexity of Soft Matters
• Chapter 5 Static Electrorheological Effect
• Chapter 6 Dynamic Electrorheological Effects
• Chapter 7 Granular Systems