Cyclopolymerization of 1,6-heptadiyne derivatives containing the bulky substitutents was carried out by metathesis catalyst systems. The catalytic activity of molybdenum (V) chloride (MoCl5) in homopolymerization is greater than that of the MoCl5- cocatalyst system, and copolymerization is vice versa in catalytic activity. Newly synthesized homo- and copolymers were soluble in common organic solvents and could afford thin film by solution-casting onto the indium-tin oxide coated glass substrate. The NMR, Fourier transform infrared spectroscopic, and UV-visible spectra indicated that these polymers have a linear conjugated cyclic polyene structure having a bulky substitutent as a pendant group. The number-average molecular weight of these polymers was in the range of 2.4-6.27 x 10(3). The copolymers exhibited a relatively higher molecular weight than that of the homopolymers. The copolymers were stable up to 380 degreesC. The electrical conductivities of the I-2-doped copolymer thin film by the four-point probe method and surface plasmon resonance spectroscopy were about 500 and 600 S/cm, respectively.