Manipulation of clusteroluminescence in cholesterol-based liquid crystal polymers

Non-conjugated cluster luminescent materials have attracted much attention due to their great theoretical significance and potential applications in different areas. Despite great progress have already achieved, it is still challenging to regulate their photo-physical properties by manipulating aggregated structure. In this work, two cholesterol-based liquid crystal polymers PMJ0Chol and PMJ6Chol with different flexible spacer length were synthesized. The aggregated structures and photo-physical properties were systematically studied. Due to the different flexible spacer length, the coupling effect between the main chain and side groups varies, and the two polymers exhibit different liquid crystal phase structures. PMJ0Chol forms columnar nematic liquid crystal, while PMJ6Chol forms more compact and ordered smectic liquid crystal. PMJ0Chol and PMJ6Chol inherit the clustering-triggered emission characteristic of cholesterol and the luminescence behavior exhibits significant excitation wavelength dependence. However, the difference in aggregated structure also leads to changes in photo-physical properties. PMJ6Chol shows more red-shifted fluorescence luminescence, and room temperature phosphorescence with 293 ms long life time is observed.