An artificial molecular chaperone: poly-pseudo-rotaxane with an extensible axle.

Poly-pseudo-rotaxanes CDs contains as a subset 1 (CDs; cyclodextrins, 1; poly(delta-valerolactone) having single beta-CD at the end of the polymer chain) initiate polymerization of delta-valerolactone (delta-VL) in the solid state when CDs (alpha-CD, beta-CD, and 2,6-di-O-methyl-beta-CD) are threaded onto the polymer chain. 1 without threaded CDs did not show any polymerization ability for delta-VL. An adamantane molecule (Ad) inhibited the polymerization ability of CDs contains as a subset 1 for delta-VL, indicating that beta-CD at the end of CDs contains as a subset 1 could not bind delta-VL because the beta-CD cavity was occupied by Ad. It should be noted that the insertion reaction and the polymerization took place inside the beta-CD cavity at the end of CDs contains as a subset 1 and that the formation of poly-pseudo-rotaxane is necessary for the initiation of delta-VL. The structures of beta-CD contains as a subset 1 and 1 were characterized by powder X-ray diffraction measurements and solid-state NMR spectroscopies. The polymer chain of beta-CD contains as a subset 1 was found to elongate in the solid state, whereas the polymer chain of 1 formed a random coil conformation. 1 was deactivated for the polymerization by blocking the active cavity of beta-CD with the polymer chain. CDs threaded onto 1 are immune to the initiation of delta-VL directly but have an essential role to fold the polymer chain in a proper way as an artificial chaperone.