Host-Guest Complexation-Triggered Chiroptical Change of Poly(phenylacetylene)s Bearing Binaphthocrown Ether Moieties on the Main Chain

Diacetylene monomers with respective lengths of the oxyethylene chains were cyclopolymerized with a rhodium catalyst to produce novel poly(phenylacetylene)s bearing a different cavity size of the chiral crown ether in the repeating units (2a-c). In the circular dichroism spectra of the resulting polymers, characteristic Cotton effects were observed in the range from 350 to 500 nm corresponding to the absorption of the conjugated polymer backbone, indicating that the polymers possessed a helical structure with an excess single screw sense induced by the covalently bonded binaphthyl units. The host-guest complexation of 2a-c with achiral guests produced a chiroptical change based on the fluctuation in the main chain conformation. The behavior of the complexation-induced chiroptical change was essentially dictated by the cavity size of the binaphthocrown ether units. Additionally, a chirality-responsive helicity change was observed in the case of the complexation of 2a-c with chiral guests, which also depended on the crown ether size. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1197-1206, 2010