Abstract Six homologous series of novel ferroelectric liquid crystals containing α-methylcinnamoyl moiety in the core structure: (Remark: Graphics omitted.) (IA: k=1, l=1, (Remark: Graphics omitted.), n=8–16; IB: k=1, l=1, (Remark: Graphics omitted.), n=8–16; IIA: k=1, l=2, (Remark: Graphics omitted.), n=9–16; IIB: k=1, l=2, (Remark: Graphics omitted.), n=8–14, IIIA: k=2, l=1, (Remark: Graphics omitted.), n=9–16; IIIB: k=2, l=1, (Remark: Graphics omitted.), n=9–16) have been synthesized and their thermal and ferroelectric properties have been investigated. The mesomorphic transition temperatures and the spontaneous polarization for the homologous series (IA, IB, IIA, IIB, IIIA, and IIIB) depend on the core structure, the chiral group, and the terminal alkoxyl chain length. These homologous series show the chiral smectic C phase over wide temperature ranges including room temperature and the values of their maximum spontaneous polarization are in the range of 30 to 800 μCm−2. The thermal stability of the mesophase and the magnitude of the spontaneous polarization have been discussed from the view point of the molecular structure and the local molecular interactions.