Helicity Control of Polymeric Backbones with Alternating cis‐trans Double Bonds in Cyclopolymerized Dipropargyl Amides

We report the synthesis of new helical polymeric structures having alternating cis and trans double bonds and chiral amino acid side chains by metathesis cyclopolymerization. The polymer helicity, which is generated by the interaction between fluorenylmethyloxycarbonyl (Fmoc) groups in the side chains, is dramatically affected by solvents. A thorough experimental and theoretical analysis including nuclear magnetic resonance, atomic force microscopy, and density functional theory and molecular mechanics calculations suggests that the helicity of both backbone and side chains are determined by anti‐syn rotation of the carbamate groups and by the different interactions of the Fmoc groups with solvents. A conjugated polymer synthesized from dipropargyl amides of fluorenylmethyloxycarbonyl‐protected amino acids by metathesis cyclopolymerization exhibits a precise alternating cis‐trans double bond arrangement with strong solvent‐dependent helicity. A P‐helix is obtained in chloroform, an M‐helix in N,N‐dimethylformamide, and none in tetrahydrofuran.