Synthesis and optical properties of chiral polydiacetylenes

Chiral diacetylenes featuring ester and urethane groups are readily prepared from amino acids and diynediols. The ability of the butadiyne moiety to undergo topotactic polymerization is dependent on both the length of the chain to the urethane group and the size of the amino acid. In some cases, the polymerization proceeds as well as the well-studied achiral parent compound, 4BCMU. The polymers form yellow solutions in good solvents where the chains adopt a random-coil configuration. Addition of a nonsolvent changes the solution color to red as the chains adopt a helical conformation.