Reaction of di(p-isocyanatophenyl)methane (MDI, 4) with N,N'-di(2-hydroxyethyl)- (1b) or N,N'-di[2-(2'-hydroxyethoxy)ethyl]-4,4'-bipyridinium di(hexafluorophosphate) (1e) and other diols [oligo(ethylene glycol)s and poly(tetramethylene oxide)s] in the presence of bis(p-phenylene)-34-crown-10 (2) afforded polyurethane (pseudo)rotaxanes as statistical (7P or 7R) and segmented analogs 10P (P = pseudorotaxane, R = rotaxane). In 7R a bulky alcohol was incorporated at the chain ends and in 13R a bulky diol as in-chain units to form polyrotaxanes and preclude the possibility of dethreading. The crown ether 2 in 10P and 13R was shown by H-1 NMR spectroscopy to be shuttling between the viologen (paraquat) and urethane sites; in DMSO the crown ether prefers the urethane site, probably because of H-bonding with the N-H moieties and complexation of the pyridinium site by the dipolar solvent, while in acetone at low temperatures the viologen site is preferred by the crown ether, with Delta H = -6.91 kcal/mol and Delta S = -22.9 eu for 13R. (C) 2014 Elsevier Ltd. All rights reserved.