The monolayer behavior of three newly synthesized side-chain liquid crystalline polysiloxanes and corresponding monomers have been investigated at the air/water interface. The surface pressure-area isotherms and Brewster angle microscopy (BAM) were used to study the influence by different mesogenic units in the side chains. The results indicate that difference in mesogenic unit structure, such as linkage bond and mesogen length, have marked effects on the liquid crystallinity and self-aggregation tendency of the molecular chains which determine the properties of the monolayers.