Dibenzo-24-crown-8-terminated polystyrene (5) was chain extended to "dimeric" 8 by pseudorotaxane formation with a ditopic guest, alpha,omega-bis[p-(N-benzylamrnoniomethyl)phenoxy]heptane bis(hexafluorophosphate) (7). The three-armed star polymer 11 was similarly formed by complexation of the dibenzo-24-crown-8-terminated polystyrene (5) with a tritopic secondary ammonium salt, 1,3,5-tris[p-(benzylammoniomethyl)phenyl] benzene tris(hexafluorophosphate) (10). Another three-armed star polymer 13 was self-assembled from dibenzo-24-crown-8-terminated polystyrene (5) and a tetratopic paraquat compound, 1,2,4,5-tetrakis{p-N-[(N'-methyl-4,4'-bipyridinium)methylphenyl]}benzene octakis(hexafluorophosphate) (12). The above chain extension and star polymer formation processes seemed to be cooperative; that is, the second and third complexation steps proceed with stepwise higher efficiencies than statistically expected. Dibenzo-24-crown-8-terminated polystyrene (5) was chain extended with secondary ammonium terminated polystyrene 14, forming 16, and also self-assembled with a secondary ammonium ion terminated polyisoprene 15 to form supramolecular block copolymer 17. These processes were examined by NMR, mass spectrometry and viscometery. Thus, although binding in these systems is not particularly strong (association constants <10(4) M-1), these examples provide proof-of-principle that pseudorotaxane formation is a viable concept for chain extension and self-assembly of novel types of block copolymers and star polymers. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3518-3543, 2009