TGBs below SmA*: Mesophase behaviours and optical properties.

[Display omitted] • Re-entrant behaviours, which were rarely reported for pure matters of dimeric liquid crystals, were analyzed. • Relaxation effects play an important role during the cooling process from a SmA* phase to a TGB phase. • An abnormal phase transition of TGBC*-SmA* was analyzed. • The selective reflection wavelength of re-entrant TGBA blue shifts to the visible light range by doping method. • This series of dimers are compared with other series to study the structure–property relationship. Re-entrant mesophase behaviours are studied including the relaxation effect of TGB phases, and an abnormal phase transition of TGBC*-SmA*. For the re-entrant TGBA mesophase between SmA* and TGBC*, its temperature range can be expanded by doping method and meanwhile its selective reflection wavelength moves to the visible light range. Furthermore, this series of dimers are compared with other series to study the structure–property relationship. This research provides an important reference for preparing materials exhibiting multiple mesophases that reflect visible light within multiple temperature ranges. [ABSTRACT FROM AUTHOR]