N-Propargylamides with bulky pendent groups [HCequivalent toCCH(2)NHCOR, 9: R = CH2C(CH3)(3), 10: R = C(CH3)(3), 11: R = C(CH3)(2)CH2CH2CH3, 12: R = CH(CH2CH3)(2), 13: R = CH(CH2CH2CH3)(2)] were polymerized with a rhodium catalyst, (nbd)Rh+B-(C6H5)(4) (nbd = 2,5-norbornadiene), to obtain the polymers in 80-92% yields. Poly(11) and poly(12) possessed moderate molecular weights (M-n greater than or equal to 10000) and were totally soluble in a few solvents including chloroform. On the other hand, the M. values of poly(9), poly(10), and poly(13) were no more than 5000, and these polymers were not completely soluble in any solvents. The conformational transition behavior of these polymers was examined by temperature-variable UV-vis spectroscopy in chloroform solution, which revealed that poly(10)-poly(13) could form dynamically stable helical conformation even at 60 degreesC. By copolymerizations of monomers 9 and 10 with monomer 4, HCequivalent toCCH(2)NHCO(CH2)(4)H, the solubility of the polymers was effectively improved and almost all the copolymers totally dissolved in chloroform, while the molecular weights of the copolymers increased up to 18600-45000. Moreover, the helix contents of poly(4(0.63)-co-9(0.37)) and poly(4(0.40)-co-10(0.60)) were the highest among the two series of (co)polymers, respectively. It is concluded that the copolymerization of 9 and 10 with 4 effectively decreased the steric repulsion between the crowded side chains, which probably allowed the copolymers to take helical conformation efficiently.