A new class of thermotropic side-chain liquid crystalline polymers containing a poly(1,6-heptadiyne) main chain was prepared by metathesis polymerization with transition-metal catalysts. It was found that the MoCl5-based catalyst systems were very effective for the cyclopolymerization of presently investigated monomers. Resulting polymers exhibited good solubility in common organic solvents such as tetrahydrofuran (THF), chloroform, etc., and could be easily cast on glass plates to give black shiny thin films. The structure of the products was confirmed by IR, MS, UV-visible, and H-1 and C-13 NMR. The number-average average molecular weight (M(n)) values of the polymers were in the range of 4.9 X 10(3)-1.1 x 10(5) relative to polystyrene standards by GPC. Thermal behavior, morphology, and electrical conductivity were investigated by using differential scanning calorimetry (DSC), cross-polarized optical microscopy, X-ray diffraction analysis, and an LCR meter. Both monomer and polymer displayed enantiotropic liquid crystallinity showing the reversible phase transitions. Room-temperature conductivities of the undoped and I2-doped polymers were found to be about 10(-11) and 10(-2)-10(-3) S/cm, respectively.