Synthesis and Helical Structure of Poly(1‐methylpropargyl ester)s with Various Side Chains

Optically active 1‐methylpropargyl esters bearing various substituents were polymerized with [(nbd)Rh] + [η 6 ‐C 6 H 5 B(C 6 H 5 ) 3 ] − (nbd=norbornadiene) as a catalyst to afford the corresponding poly(1‐methylpropargyl ester)s with moderate molecular weights in good yields. The polymers have a cis ‐stereoregular structure, which was determined by 1 H NMR spectroscopy. Large optical rotations and clear CD signals demonstrated that all these polymers take on a helical structure with a predominantly one‐handed screw sense. The polymers exhibited large viscosity indices in the range 1.14–1.75. Chiral amplification was observed in R / S copolymerization. Conformational analysis revealed that the polymers form a tightly twisted helical structure with a dihedral angle of 70° at the single bond of the main chain.