DNA-like Double Stranded Polymers

The synthesis of a series of helical double strand polymers containing ferrocene moiety by ring opening metathesis polymerization (ROMP) of a bisnorbornene derivative is described.　Ferrocene moiety was incorporated as part of the linker since it has certain rigidity but is somewhat flexible. 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 STM and simulated by molecular mechanical and dynamical calculations. The polymer thus obtained resembles structurally 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. These results suggest that the polymers may adopt our proposed DNA-like double stranded structures.
On the other hand, A series of chiral double stranded polymers were designed and synthesized. Between chromophores interaction may occur as evidenced by the blue shift of the absortion maximum. A pair of enantiomeric double stranded monomers and polymers was subjected to CD measurements. Substitute of chiral center may appear to be the pivotal factor to dictate the CD properties of chiral double stranded monomers and polymers. The CD intensity of chiral double stranded polymers is enhancement than monomers. These results suggest that the helixty of chiral double stranded polymers may increased.