Synthesis and Characterization of Poly[3]rotaxane through the Mizoroki-Heck Coupling Polymerization of Divinyl-functionalized [3]Rotaxane

Abstract

Main chain-type poly[3]rotaxanes were synthesized according to the rotaxanation-polymerization protocol by the polymerization of a divinyl [3]rotaxane monomer through the Mizoroki-Heck coupling with a diiodoarene. [3]Rotaxane 5 consisting of two monovinyl dibenzo-24-crown-8-ether wheels (2) and sec-ammonium salt (3) as an axle component was synthesized in 86% yield by a typical urethane end-capping reaction of the axle terminal hydroxyl group with bis(4-isocyanophenyl)methane in the presence of a catalytic amount of di-n-butyltin dilaurate. Quantitative N-acetylation of 5 yielded mono(vinylphenyl)-functionalized wheel-containing [3]rotaxane monomers 6. The mobility of the wheel components in [3]rotaxanes was evaluated by the two-dimention NOESY spectra of 5 and 6. The main-chain type poly[3]rotaxanes 8 were obtained in high yields by the Mizoroki-Heck-type polycondensation of 6 and diiodoarenes 7 in the presence of a palladium catalyst (Pd(OAc)2). The structures of the polyrotaxanes were determined mainly by NMR and GPC, while the IR spectra showed that vinylene groups formed mainly took the trans configuration. Properties of the polyrotaxanes such as solubility and thermal stability were evaluated.