A new series of cyano-substituted mesomorphic side chain polyacrylates has been synthesized. Optical observations, D.S.C. studies and X-ray diffraction on oriented samples show that all polymers possess a partially bilayer Sadphase. The smectic period has been measured from which it is inferred that the molecular structure of the mesogenic cores (i.e. the presence of pH-systems and antiparallel dipoles) induces a small overlap (d≊ 1·71). The X-ray patterns show that for the whole series, the third order reflection is the most intense. By inverse Fourier transform, we derive the projection of the electron density profile along the director which we try to explain in terms of the molecular features.