Published papers

In this study, we investigate the morphology and phase diagram of self-assembled polymeric nanoparticles (NPs) confined within nanotubes (NTs) by dissipative particle dynamics simulations. There is a clear relationship between the self-assembling architecture of nanoparticles (NPs) and their physical properties, and Polymer-tethered NPs, which are created by grafting polymers onto NPs to control the self-assembly of NPs, have attracted considerable attention. However, self-assembled structures have not been systematically classified because of the large number of tuning parameters such as the polymer length and graft density. In this study, we investigated the confinement of NPs grafted with three types of polymers: hydrophilic, hydrophobic and Janus surface, hydrophilic and hydrophobic walls. First, we derived the qualitative phase diagram of the axial pressure Pz and the ratio L of NT radius to NP radius. As a result, in polymer-grafted NPs with Janus amphiphilic surface, hydrophobic and hydrophilic polymer tether NPs were found to assemble axially to form an ordered structure, and in hydrophobic NTs, a double helical structure was formed at L=3.0. These simulation results show that the self-assembled structure of polymer tether NPs can be qualitatively predicted based on the chemical properties of NT walls and the surface design of polymer tether NPs.

Fluids confined in nanochannel exhibit distinct phases and flow properties not shown in the bulk. These confined systems are involved in many industrial and engineering applications such as nanofluidic devices, biological membranes and therefore understanding and controlling the molecular behavior of confined liquids is important. Octamethylcyclotetrasiloxane (OMCTS) is a small macrocycle made of four covalently linked Si(Me)2O units which have been used as a model liquid in the experimental studies. However, much less is known about the mechanisms related to external stimuli such as shear and how those molecular behaviors in a confined system impact the flow properties of the whole liquid. In this study, we have investigated the structure and shear viscosity of OMCTS confined between two mica walls under shear, using molecular dynamics simulation. The results showed layering of OMCTS molecules, depending on the distance between two mica surfaces. In addition to this, the structural changes were observed accompanied by shear-thinning behavior when we applied shear to the system.