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](+) [eta(6)-C6H5B(C6H5)(3)](-) (nbd = norbornadiene) as a catalyst to afford the corresponding poly(1-methylpropargyl ester)s with moderate molecular weights in good yields. ne polymers have a cis-stereoregular structure, which was determined by H-1 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 degrees at the single bond of the main chain.