Cholesteric liquid crystals (CLCs) are a significant class of temperature-responsive photonic materials that have the ability to selectively reflect light of a specific wavelength. However, the fabrication of main-chain CLC oligomers with dramatic reflection band variation upon varying the temperatures remains a challenge. Here, a feasible method for improving and controlling the responsiveness of main-chain cholesteric liquid crystal oligomers by the incorporation of a smectic monomer is reported. The smectic monomer strengthens the smectic character of the oligomers and enhances the magnitude of the change of the pitch as a function of temperature upon approaching the cholesteric–smectic phase transition temperature. The central wavelength of the reflection band can be easily modified by mixing in an additional chiral dopant. This promising method will open the door to the preparation of temperature-responsive photonic devices with excellent responsiveness.

Cholesteric liquid crystal oligomers and polymers are promising materials for creating materials and devices with stimuli-responsive structural color, and the cholesteric to smectic pre-transition effect is of particular interest as it leads to a strong redshift in the reflected color upon cooling. Cholesteric polymers can be stabilized by the formation of semi-interpenetrating networks to obtain more robust photonic materials, but this tends to strongly suppress the pre-transition effect. Here, we show that the pre-transition effect in semi-interpenetrating networks based on main-chain cholesteric oligomers can be amplified by incorporating a smectic monomer and by increasing the degree of polymerization of the oligomers. This amplification counteracts the suppressing effect of the semi-interpenetrating network, and the resulting materials still show a significant band shift upon cooling. Presumably, both methods lead to the formation of more smectic domains in the cholesteric helix, which causes an amplified pre-transitional effect. The results bring us closer to the use of cholesteric semi-interpenetrating cholesteric networks for applications in smart sensing, healthcare, and safety devices.