Poly (1,6-heptadiyne) derivatives substituted with long side chains containing mesogen units such as poly(bis(4-methoxy-4′-hexyloxybiphenyl)- dipropargyl malonate) (PMHBDPM) exhibit unique characteristics typical to both liquid crystal and conducting polymer. PMHBDPM exhibits smectic A phase in consistent with temperature dependence of X-ray diffraction. Two stages of electrochemical doping corresponding to the charge transfers between dopants and polymer main chain and also between dopants and the core of the mesogen unit in the side chain are observed. Diffusion coefficient of dopants also exhibits drastic change at the phase transition between smectic A phase and isotropic phase. These characteristics have been discussed in terms of molecular orientations of both polymer main chains and substituted side chains. Unique dielectric properties and X-ray diffraction characteristics have been observed in a mixture of PMHBDPM with ferroelectric liquid crystal of low molecular weight.