Helicity control of poly(phenylacetylene) bearing polycarbohydrate ionophore as graft chain

End-functionalized (1&rarr6)-2,5-anhydro-3,4-di-O-ethyl-D-glucitol, macromonomer 2, was synthesized by the cyclopolymerization of diepoxide monomer 1, followed by treatment with 4-ethynylbenzoyl chloride as a terminating agent. The copolymerization of 2 with phenylacetylene 3 yielded poly(phenylacetylene) bearing polycarbohydrate ionophore as the graft chain, 4. The CD spectrum of 4 showed Cotton effect in the long wavelength region of the polyacetylene backbone. This suggested that 4 had a predominantly one-handed helical conformation induced by the chirality of the carbohydrate polymer as the graft chain. In addition, the helical conformation of 4 was inverted by forming a complex between the macromolecular ionophore unit and metal cations, which was the first example of the helix-helix transition induced by an achiral inorganic molecule.