A pure deformed helix ferroelectric liquid crystal (DHFLC) material viz. MOPBIC with antiferroelectric (AF) phase, having high spontaneous polarization (P-S) and short pitch, is found to show large dielectric constant (epsilon') which increases with increasing cell thickness. The molecular contributions from different bonds, groups and conformers to the dipole moment and the deformed helix configuration of the typical molecular structure of MOPBIC are attributed to these high values of P-S and epsilon'. MOPBIC also exhibits high speed optical response over a wide temperature range and the frequency dependent memory effect. (c) 2007 Elsevier B.V. All rights reserved.