The thioester unit has been commonly used to enhance the mesophase thermal stability and phase range in numerous liquid crystal materials. In this paper we report the synthesis of a homologous series of thioesters with similar structures to AS620 {(S)-(+)-1-methylheptyl 4-[5-(4-dodecyloxyphenyl)thien-2-ylcarbonyloxy]benzoate, 10d in this paper}. A complex phase morphology is observed that indicates an anti-ferro-anti phase sequencing [for the octyloxy derivative (9a in this paper)] based on electrooptic evaluation and especially the observation of polarization threshold on either side of the ferroelectric phase.