Vinyl Ketones Containing Fluorene Skeletons for Acrylic Resins with High Refractive Index and Negative Birefringence

Abstract

The radical (co)polymerization of 2‐acryloylfluorene (1a) and 2‐acryloyl‐9,9‐dimethylflureoene (1b) with methyl methacrylate and the thermal and optical properties of the resulting (co)polymers are investigated. Because the two methyl groups at the 9‐position prevent the interaction of aromatic rings, the solubility is drastically improved for the homopolymer of 1b. The incorporation of 1b‐units increases both the glass transition temperature (118°C–170°C) and 5% weight‐loss temperature (289°C–354°C). In addition, the refractive index of the polymers at 589 nm increases from 1.49 to 1.65 with higher mole fractions of 1b‐units, whereas the negative birefringence significantly increases. These features are attributed to the restricted bond rotation of the rigid aromatic pendant groups bound to the backbone via an sp2 carbon atom (carbonyl group).