Clustering‐Triggered Emission Liquid Crystalline Polymer Bearing Cholesterol: Tunable Circularly Polarized Luminescence and Room‐Temperature Phosphorescence

• Published in: Macromolecular rapid communications. 2023-12, Vol.44 (24), p.e2300449-n/a
• Main Authors: Zhou, Mengdie, Zhang, Jiafan, Chen, Yueyue, Chen, Zhong, Yuan, Yongjie, Gong, Yongyang, Zhang, Hailiang
• Format: Article
• Language: English
• Subjects: Afterglows; Chirality; Cholesterol; cholesterol liquid crystal polymers; Circular polarization; circularly polarized luminescence; Cluster Analysis; Clustering; clustering‐triggered emission; Coatings; Crystals; Emission; Emissions; Heterogeneity; Liquid crystal polymers; Liquid crystals; Luminescence; Phosphorescence; Polymer films; Polymers; room‐temperature phosphorescence; Temperature
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.202300449

Circularly polarized luminescence (CPL) materials with clustering‐triggered emission (CTE) characteristic have gradually attracted attention for their unique photophysical properties. However, the majority of reported clusteroluminogens lack chirality and exhibit heterogeneity, making it challenging to achieve a well‐defined helical structure necessary for efficient CPL with high dissymmetry factor (glum). In this paper, chiral liquid crystals are constructed to obtain CTE‐based CPL materials with high glum values. Side chain liquid crystal polymer PM6Chol bearing cholesterol clusteroluminogens are designed and synthesized. PM6Chol‐coated film and PM6Chol thermal‐treated film are also successfully prepared by different film‐forming methods. Both the films inherit the CTE characteristic of cholesterol and show excitation wavelength‐dependent luminescent behavior. However, the two polymer films exhibit different liquid crystal phase structures, with PM6Chol‐coated film being a chiral bilayer smectic C phase and PM6Chol thermal‐treated film being an achiral bilayer smectic A phase. Attributed to helical arrangement of cholesterol, PM6Chol‐coated film emits efficient CPL with glum values up to 1.0 × 10−1. For PM6Chol thermal‐treated film, no CPL signal is detected due to the absence of helical structure. However, it shows obvious room‐temperature phosphorescence with 2.0 s afterglow and 23.9 ms lifetime. The influence of film‐forming method on the phase structure and photophysical properties of PM6Chol are presented. PM6Chol‐coated film exhibits an arrangement of SmC* and demonstrates excellent circularly polarized luminescence (CPL) based on clustering‐triggered emission. However, the phase structure undergoes a transition from SmC* to SmA after thermal treatment, PM6Chol thermal‐treated film exhibits silent CPL and shows room‐temperature afterglow.