We achieved a highly efficient one-pot synthesis of permethylated R-cyclodextrin(CD)-based polyrotaxane via an initial complexation to the inclusion complex with amine-terminated polytetrahydrofuran followed by end-capping with a bulky isocyanate in hydrocarbon solvent under heterogeneous conditions. Among various organic solvents tested, isooctane was the best solvent, while cyclohexane yielded no polyrotaxane. Effects of the reaction temperature, the molecular weight of the axle polymer, the structures of the wheel and axle components on the yield and coverage ratio of the polyrotaxane were studied in detail. Under the optimum conditions, we obtained a 71% yield of polyrotaxane with a 67% coverage ratio when amine-terminated poly(tetrahydrofuran) (M n 8700) reacted with permethylated R-cyclodextrin at 50°C in isooctane. We discuss the reason for and the mechanism of the efficient reaction that occurred in the heterogeneous system from the viewpoint of the role of the solvent and the results of the solvent-free synthesis previously reported. By a similar one-pot reaction, polyrotaxane consisting of permethylated R-cyclodextrin and poly(ethylene glycol) was first synthesized. Neither native R-CD nor permethylated β-CD gave any polyrotaxanes when amine-terminated poly(tetrahydrofuran) was used as an axle polymer.

The directed synthesis of main chain-type polyrotaxanes possessing crown ether wheels was successfully achieved through two methods, A and B. Method A involved the direct wheel threading of poly(sec-ammonium salt) followed by end-capping with a bulky group, while method B utilized polyaddition of a pseudo[2]rotaxane monomer to facilitate the control of the structure, i.e. the rotaxanation ratio.

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