|many materials in this class are not soft to the touch. It is better defined as "mesoscopic matter" since the size of the basic constituents ranges from a few nano-meters to about one micro-meters (Fiugre 12-35a) - at the boundary between quantum and classical objects (Figure 12-35b). It is the properties and interactions of these mesoscopic structures that determine the macroscopic behavior of the material; the quantum
Figure 12-35a Soft Matter
Figure 12-35b Length Scale
|effect in the atomic or molecular scale are unimportant. Some examples for the soft matter are listed below.
Table 12-07a Colloids
Figure 12-35c Polymer Structure [view large image]
|in a liquid, these chains wind into little balls. In the presence of large numbers of chains and depending on the process of production, they can grow intertwined into a kind of solid like the plastics shown in Figure 12-35c, diagram d and Figure 12-35a.
|Most polymers are in either amorphous or semi-crystalline forms. Depending on temperature, they can also exist in rubbery and melt states (Figure 12-35d). Thermo-plastics do not undergo chemical change in their composition when heated and can be
Figure 12-35d Polymer Properties [view large image]
Table 12-07b Plastics Families [view table]
|moulded repeatedly. Thermosets type plastics can melt and take shape once; they stay solid after solidification.
Figure 12-35e Vesicle
Figure 12-35f Emulsion
Figure 12-35g Emulsion Examples [view large image]
Figure 12-35h Liquid Crystal Phase
Figure 12-35i Liquid Crystal Examples [view large image]
|between the molecules. Actually, in the meso-phase the 3-dimensional ordering has been reduced to 1 or 2-dimensional ordering (Figure 12-35h). Figure 12-35i shows the various types of liquid crystals.
|Liquid crystals find wide use in liquid crystal displays, which rely on an electric field to control its orientation. Polarization of the light depends in turn on the orientation so that it is either blocked or transmitted by a second polarization filter (polarizer) perpendicular to the first one (Figure 12-35j). The liquid crystal in this application is usually the nematic type (rod-shaped) in twisted form at relaxing state.
|Legend for Figure 12-35j: L - light, P1 - horizontal polarizer, P2 - vertical polarizer, E1, E2 - electrodes, LC - liquid crystals, G -grid, V - voltage supply, S - switch, I - image.
Figure 12-35l Organic Compounds [view large image]
|2. DNA and RNA are also polymers made from nucleotides (the monomers). In a biological system the combination of the mono-mers cannot be at random. It has to be very specific and coiled up into chromosomes, otherwise the organism would not survive.