Modular 9,9-Substituted Fluorene Cardo Design for Thermoplastic High-Refractive-Index Polymers with Low Birefringence

Cardo structures are applied extensively for the preparation of high refractive index polymers (HRIPs) with intrinsically low optical anisotropy. While such design allows for the achievement of low birefringence, the refractive indices of cardo-based polymers have been largely limited to below 1.70. We report herein a modular cardo design based on 9,9-diarylfluorene bearing sulfur-containing aromatic substituents at the C-9 position and polymerizable handles at the 2,7-positions. Applying variou