Novel side-chain liquid crystalline polymers were synthesized based on the molecular design of the chemical structures of main-chain, spacer, and mesogenic groups. The main-chain structure is polydiene by the radical polymerization of diene derivatives with a mesogenic group. Spacer groups are not only oligomethylene but also those containing a siloxane or ether Linkage. The stereochemistry of the main chain, elucidated by H-1 NMR, C-13 NMR, DEFT, and NOESY spectroscopies, is principally (E)-1,4 (cis concerning the carbon-carbon main chain). The polymers take the smectic Liquid crystalline state with cyanobiphenyl, fluorobiphenyl, or alkoxybiphenyl as a mesogen. The transition temperatures of polymers with a spacer having a siloxane linkage are lower than those with hexamethylene as a spacer. Cooling the polymer with 4-(hexyloxy)biphenyl as a mesogen and siloxane linkage in the spacer seems to result in the change of the phase which is evidenced by the change in the optical polarization micrograph.