The molecular self-assembling with topological characteristics has recently attracted interests of many researchers. A typical example is a polyrotaxane, necklace-like supramolecule of cyclic molecules threaded onto an axis polymer chain.
In the polyrotaxane, a polymer chain and cyclic molecules are topologically confined to each other, which drastically changes the movement and entropy of the chain and cyclic molecules.
We have investigated the motion, conformation and entropy of polyethylene glycol as an axis polymer and cyclodextrins as cyclic molecules in a polyrotaxane, and found new phenomena such as molecular phase separation in polyrotaxane. This leads to creating various novel polymeric materials with peculiar nano-scale structures and functions such as molecular motor and so on.