A racemic mixture and two chiral monomers of 2-methyl-1-butyl propiolate, i.e., rac1, R1, and S1, were stereoregularly polymerized with a catalyst, [Rh(norbornadiene)Cl](2), in methanol at 40 degrees C to obtain the corresponding helical racemic and two chiral polymers, Prac1, PR1, and PS1, and a copolymer, Pco. The 1H and 13C NMR spectra of the racemic and chiral polymers differed, although the NMR spectra of their monomers were the same. The structures of the Pco copolymers with different chiral monomer ratios were analyzed using 1D and 2D NMR, optical rotation, circular dichroism (CD), UVvis, and computational methods to elucidate the stereochemical effect of the chiral monomers together with the polymerization mechanism. The temperature dependence of H-1 and C-13 NMR spectra in line shape and intensity indicated that the helical main chain undergoes restricted rotation around the ester methylene bonds -OCH2 through a three-site jump exchange called an accordion-like helix oscillation (HELIOS). The energetically preferred structures of the helical-sense polymers PR1 or PS1 were simulated using the MMFF94 program. The dependence of the NMR spectral line shapes, optical rotations, and calculated structures on the monomer feed clearly indicated that the copolymers alternatively incorporate R1 and S1 to generate one-handed helical-sense chains. Based on these results, a polymerization mechanism is proposed, explaining a strictly alternating copolymerization that yields helical chains.