Novel optically active polyacetylene derivatives exhibiting liquid crystallinity; liquid crystal compositions containing the derivatives; and moldings thereof. Specifically, polyacetylene derivatives which have helical structure of rigid-rod shape and which exhibit a liquid crystal phase either in a solvent containing an organic solvent as the main component or in a molten state as well as electric field orientation; liquid crystal compositions containing the derivatives; and moldings thereof. More specifically, polyacetylene derivatives having helical structure of rigid-rod shape as represented by the general formula [1]; liquid crystal compositions containing the derivatives; and moldings thereof: wherein R1 and R2 are each independently aminocarbonyl of an amino acid having an ester linkage with C2-22 alkyl or carbonylamino of an amino acid having an amide linkage with C2-22 alkyl, the amino acid being achiral one, or chiral one of (S)- or (R)-configuration, or a racemic mixture composed of both antipodes; and X is a number satisfying the relationship: 0