A STRATEGY TO ELIMINATE DETHREADING DURING THE PREPARATION OF POLY(ESTER CROWN ETHER ROTAXANE)S - USE OF DIFUNCTIONAL BLOCKING GROUPS/

A novel strategy to completely eliminate dethreading of captured cycli cs during the preparation of polyrotaxanes has been developed. A new d ifunctional blocking group (BG), namely is[p-((5-(chlorocarbonyl)penty l)oxy)phenyl]methane (diacid chloride BG 14), was prepared in an overa ll yield of 6% by a three-step method. BG 14 polymerized with thoxy)et hoxy)phenyl]bis(p-tert-butylphenyl)methane (diol BG 15) using 30-crown -10 (30C10) as solvent to afford poly(ester rotaxane)s 17 with unique architectures having two BGs per repeat unit. The formation of the pol yrotaxanes was proved by a chemical shift of threaded 30C10 different from that of unthreaded species, hydrolytic recovery of 30C10, and a 2 D NOESY study and supported by the GPC analysis. It was found that the resulting polyrotaxanes 17 had threading efficiencies (m/n values, av erage number of cyclic molecules per repeat unit) 2 times as high as t hose of poly(ester rotaxane)s 16 made under the same conditions from d iol BG 15 and sebacoyl chloride. By optimizing the conditions, the thr eading efficiency was increased to 0.172 in polyrotaxane 17c, almost 1 4 times as high as that (0.012) of the polyrotaxane of type 1 made fro m decanediol and sebacoyl chloride.