Preparation and thermotropic properties of partially fluorinated acrylates

New series of monomers which consist of a 4,4-biphenyl unit linked to a partially linear fluorinated chain on one side and on the other side to an acrylic part which is either directly connected to tire core or separated by an oligomethylene spacer, were synthesized. The mesomorphic properties have been characterized by light microscopy and by differential thermal analysis showing the peculiar effect of the fluorinated tail and of the spacer. The overall compounds showed an enantiotropic liquid crystal behavior. However, the series without oligomethylene unit exhibit a smectic behavior over a wide temperature range as compared to the series with a spacer where the mesomorphic behavior appear only on one degree Celsius. Increasing the lengthening of the fluorinated tail simultaneously increases the melting and the clearing points.