Pure and Applied Chemistry

Abstract: The first helical double-stranded polymer by ring-opening metathesis polymerization (ROMP) of a bisnorbornene derivative and the replication of a single-stranded polynorbornene leading to its complementary polynorbornene derivative are described. Base-promoted hydrolysis of this polymer affords the corresponding single-stranded polymer and the linker, ferrocene-1,1'-dicarboxylic acid, in excellent yield. Three forms (helical, supercoil, and ladder) of the polymer have been observed by scanning tunneling microscopy (STM) and simulated by molecular mechanical and dynamical calculations. The polymer thus obtained has a structural resemblance to DNA by having similar width, number of monomeric units per pitch, five-membered rings in the polymeric frame, perpendicular linkers to the backbones, and similar spacing between neighboring monomeric units. In the replication study, the single-stranded polynorbornene acts as a template for norbornene monomer adhesion via ester linkage. This polymer is treated with Grubbs-I catalyst to proceed the ROMP to afford the corresponding unsymmetric double-stranded polymer. After hydrolysis, a complementary polynorbornenecarboxylic acid is produced. This approach may provide a versatile entry for the design, synthesis, and physicochemical investigations of new types of polymers for simulation of biological systems as well as materials applications.