Cover Image, Volume 50, Issue 10


original image

α-Proparygl amino acid derived polyacetylenes containing unprotected carboxy groups adopt predominantly one-handed helical conformations, as presented by H. Sogawa, M. Shiotsuki, and F. Sanda on page 2008. The helical structures of the polymers are extended upon addition of alkali hydroxides (LiOH, NaOH, KOH) and tetrabutylammonium fluoride, wherein the degree of extension agrees with the order of the cation size. The existence of cations close to the carboxylate moieties results in helix loosening accompanying the extension of conjugation of the polyacetylene backbone. The polymers are expected to function as cation sensors since this ion-responsive conformational transition causes the color change of the polymer solutions that is detectable by the naked eye.