研究発表

In recent years, Janus amphiphilic nanotubes with complex surfaces have been synthesized. However, the self-assembly behavior of surfactant solutions confined in a Janus amphiphilic nanotube has not been investigated so far. We performed molecular simulations to investigate the morphologies and phase diagrams of a surfactant confined in Janus amphiphilic nanotube consisting of both hydrophobic and hydrophilic surfaces. We derived a phase diagram of the representative snapshots of equilibrium morphologies. Morphologies that were not observed in the bulk eventuated in confined systems. Moreover, the self-assembled structures were found to be dependent on the spatial confinement. Furthermore, the self-assembled structures confined in hydroneutral and Janus amphiphilic nanotubes were compared. The results suggested that the self-assembled structures confined in the Janus amphiphilic nanotube resembled that confined in the hydroneutral nanotube owing to a strong confinement effect. Our simulation offers a guide to control the rheological properties of surfactant solutions by the chemical patterns on the surfaces of nanochannels, the effect of confinement, and the self-assembled structure.

We have performed coarse-grained molecular simulation simulations to investigate self-assembly processes and structures of functionalized nanoparticles confined in a nanoslit. The functionalized nanoparticle is decorated with some attractive areas. On the basis of the observed temperature- and concentration-dependent morphologies, we derive semiquantitative phase diagrams of the temperature. Five distinct designs of the nanoparticles are considered. We find that various self-assembled structures depending on the number of functionalized groups. The self-assembly behavior of the functionalized nanoparticles can be qualitatively predicted when the number of groups is known. Our simulation offers a theoretical guide to control morphologies of the self-assembled nanoparticles, a novel system that may find applications in nanofluidic devices or for nanopatterning.

界面活性剤水溶液はバルクで様々な形態を示す．球状ミセルや棒状ミセル，紐状ミセル，二分子膜，ベシクルなどが存在することが知られている．本研究では，ナノチューブに閉じ込められた界面活性剤水溶液の自己組織化について，散逸粒子動力学シミュレーションを行った．

A telechelic polymer is an amphiphilic polymer which can form micellar structures when dissolved in water. A telechelic polymer solution shows viscoelastic behavior due to the formation of a characteristic network, i.e. loop, bridge, and dangling chain. For industrial purposes, it has been utilized for paint, cosmetics, etc. as a thickening agent. It is thus strongly demanding to predict or control its rheological properties. However, detailed studies in the molecular level have not been clarified out yet. In this study, we adopted a dissipative particle dynamics simulation method to investigate the relation between the characteristic rheological properties and the molecular structure in telechelic polymer solutions.