Helical and Luminescent Disubstituted Polyacetylenes: Synthesis, Helicity, and Light Emission of Poly(diphenylacetylene)s Bearing Chiral Menthyl Pendant Groups

Diphenylacetylenes containing chiral menthyl groups [C6H5C C-C6H4OCOCH2OR* and C6H5C C-C6H4CO2R*, R* = (1R,2S,5R)-(-)-menthyl] are synthesized and polymerized by WCl6-Ph4Sn catalyst. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, CD, and PL analyses. All the polymers are thermally stable, losing little of their weights when heated to >= 250 degrees C. They also enjoy high photostability, suffering no change in the molecular weight when exposed to UV irradiation in air for 24 h. The backbones of the polymers are induced to helically rotate by the chiral pendants, as verified by their large specific optical rotations and strong Cotton effects in the backbone absorption region in the solution and aggregate states. The polymers emit green light of 493 and 520 nm when their solutions and nanoparticle suspensions in poor solvents are photoexcited. UV irradiation of the polymer films in air photooxidizes the exposed regions, generating two-dimensional luminescent photopatterns.