Nanospheres with polymerization ability coated by polyrotaxane.

BETA-cyclodextrin (beta-CD)-based nanosphere 1 initiated the oligomerization of delta-valerolactone (delta-VL) on the surface of 1 to give oligo(delta-VL)-tethered beta-CD nanosphere 2 in bulk. Atomic force microscopy indicated that the molecular size of 2 is twice that of 1. The addition of alpha-CD to 2 leads to the formation of poly-pseudo-rotaxane on the surface of 2 to give a nanosphere with poly-pseudo-rotaxane (alpha-CD[symbol: see text]2). 2D-NOESY NMR experiments showed correlation peaks between the inner protons of alpha-CD and the oligo(delta-VL) chains in an aqueous solution, indicating that the oligo(delta-VL) chains are included in the alpha-CD cavity. Alpha-CD[symbol: see text]2 has a core of beta-CDs with poly-pseudo-rotaxanes on the surface. It should be noted that 2 did not show polymerization ability for delta-VL, but after the formation of poly-pseudo-rotaxanes, oligo(delta-VL) of alpha-CD[symbol: see text]2 repropagated upon the addition of delta-VL. Alpha-CD[symbol: see text]2 is significantly larger than nanospheres 1 and 2. Additionally, postpolymerization increases the size of alpha-CD[symbol: see text]2. These behaviors are reminiscent of the function of a spherical virus, which forms an ordered spherical structure and releases RNA chains from the capsid surface.