In these decades, amphiphilic systems are widely interested as typical systems to investigate self-organizations in soft-matter physics. A mixture of AOT, water and decane is the most popular systems in such the studies. The temperature-and pressure-induced phase transitions have been invesitigated by means of small-angle neutron and X-ray scattering and neutron spin echo. The results showed that the microscopic origins of temperature-and pressure-induced phase transitions were different, however, the effects of temperature and pressure on the semi-microscopic scale structure seemed to be the same.

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We present an overview of the modern study of soft matters from the point of view of condensed matter physics. The common feature of a soft matter is the presence of a mesoscopic length scale which necessarily plays a key role in determining properties of the system. As an example of a soft matter, we consider a microemulsion which consists of water, oil, and surfactant. Microemulsions are known to be thermodynamically stable, and show rich phase behaviors. The importance of phenomenological approaches to such a complex system is stressed by explaining lattice spin models, Ginzburg-Landau theories, and membrane curvature elasticity theories. All of these theories are successful in understanding the basic properties of microemulsions. Finally, recent experimental and theoretical findings on polymeric microemulsions are briefly reviewed.

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The soft matter such as polymers, surfactants, and colloidal particles forms a variety of ordered structures as a result of a delicate balance of energetic interactions and entropic interactions originated from the large internal degree of freedom. Recently complex systems consisting of surfactant and polymer acquire great interests because they play important roles in the field of biology, medicine, cosmetic, and food industry. In this review we introduce recent researches on the complex systems from the soft matter physics point of view. We deal with two cases, one is that polymers are introduced between lamellar bilayers of surfactant/water systems, and the other is that polymers are confined in the spherical microemulsion droplet in water/surfactant/oil ternary systems. In the case of lamellar + polymer systems, added polymers bring attractive inter-lamellar interaction due to the decrease of the conformation entropy and the depletion effect. Whereas, in the case of microemulsion + polymer systems, the confined polymers induce unique multi-stage morphology transitions as a result of a delicate balance of confining entropy of polymer chain and elastic energy of surfactant membrane. We believe that the surfactant membrane and polymer complex systems involve quite fruitful soft matter physics, which is useful to understand a variety of biological and industrial phenomena.

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