SYNTHESIS AND CHARACTERIZATION OF A POLYESTER CROWN ETHER ROTAXANE DERIVED FROM A DIFUNCTIONAL BLOCKING GROUP/

A diol with a sterically large core, namely l)bis[p-(2-(2-hydroxyethox y)-ethoxy)phenyl]methane (diol BG 7), was synthesized by a multiple st ep method and successfully used for the preparation of a sebacate-base d polyester 30-crown-10 (30C10) rotaxane with blocking groups or stopp ers along the backbone. It was found that the resulting polyrotaxane h ad a threading efficiency (m/n value, the average number of cyclic mol ecules threaded per repeat unit) 5 times as high as that without BG un der the same conditions, which proved that the BG can effectively prev ent threaded 30C10 from slipping off the polymeric backbone during the preparation of the polyrotaxane. Additionally, new evidence for the f ormation of the polyrotaxane was demonstrated, including a chemical sh ift of threaded 30C10 protons different from that of the unthreaded sp ecies, a through-space interaction between 30C10 and the backbone prov ed by 2D NOESY measurements, and hydrolytic recovery of 30C10.