A styrene‐based monomer having a five‐membered cyclic dithiocarbonate structure, 4‐vinylbenzyl 1,3‐oxathiolane‐2‐thione‐5‐ylmethyl ether (VBTE), was synthesized from 4‐vinylbenzyl glycidyl ether (VBGE) and carbon disulfide in the presence of lithium bromide in 86% yield. Radicalpolymerization of VBTE in dimethyl sulfoxide by 2,2′‐azobisisobutyronitrile was carried out at 60 °C to afford the corresponding