A poly(phenylacetylene) bearing a polycarbohydrate ionophore as a graft chain (copolymer 4) was synthesized by the copolymerization of end-functionalized (1 -> 6)-2,5-anhydro-3,4-di-O-ethyl-D-glucitol with a 4-ethynylbenzoyl group (macromonomer 2) with phenylacetylene. Copolymer 4 showed a split-type circular dichroism (CD) in the long absorption region of the conjugated polymer backbone (280-500 nm), and the CD pattern varied in response to external stimuli, such as the solvents and temperature. This suggested that 4 had a predominantly one-handed helical conformation in the polyacetylene backbone. The CD pattern of 4 was completely inverted by the formation of a complex between the macromolecular ionophore units and the selected metal cations, that is, Ba2+, Pb2+, Sr2+, Na+, and Li+. This suggested that copolymer 4 underwent a helix-helix transition through the host-guest complexation with achiral inorganic metal cations. (c) 2005 Wiley Periodicals, Inc.