Synthesis of polymers containing regularly distributed tetrathia-[7]-helicene units along the backbone

A tetrathia-[7]-helicene bearing in the 2 and 13 positions cyanovinyl groups was used as comonomer in the Michael-type polyaddition reaction with N,N'-bis(beta-mercaptoethyl)piperazine. This led to a new polymer bearing tetrathia-[7]helicene units regularly distributed along the polymer backbone, which may be regarded as the first example of a new family of potentially useful nonlinear optical materials. All products were structurally characterized by H-1 and C-13 NMR spectroscopy. Differential scanning calorimetry characterizations revealed the presence, in both monomeric and polymeric helicenes, of glass-transition like temperatures, associated to some conformational variation of the helicene units. The optical properties, the film formation and the morphology of the polymer-containing tetratia-[7]-helicenes were also investigated.