Synthesis and polymerization behavior of 1-trimethylsiloxy- or 1-triphenylsiloxysilacyclobutane derivatives were studied. These monomers gave polymers with reasonably high molecular weight by platinum catalyst like platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex. Side-chain smectic liquid crystalline polymer was obtained from 1-methyl-1-[3-{(4-cyanobiphenyl-4＇-yl)oxy} propyl]dimethylsiloxysilacyclobutane.In the polymerization by butyllithium or phenyllithium, monomers corresponding to the amounts of the initiator were consumed, but no polymers were formed. Apparently, elimination of the trimethylsiloxy or triphenylsiloxy group occurred in the nucleophilic attack of the initiator or propagating species on the silicon atom of the monomer.