Poly(phenylene thioether)s with Fluorene-Based Cardo Structure toward High Transparency, High Refractive Index, and Low Birefringence

To realize high-performance thermoplastic camera lenses for compensating chromatic aberration in which lenses with large and small Abbe numbers were combined, novel poly(phenylene thioether)s with a fluorene-based cardo structure were developed with the potential for simultaneously realizing high transparency, a high refractive index, low birefringence, and small Abbe number. Excellent transmittance was observed in all polymer films because the interchain packing was effectively suppressed by the cardo structure (e.g., transmittance was as high as 90% at 400 nm), and furthermore, high refractive index values (1.6553-1.6762) were attained. The polymer with the highest content of cardo structure exhibited a low birefringence of 0.0014. The efficient cancellation of polarization anisotropy between the polymer backbone and the fluorene units directed perpendicular to the polymer backbone contributed to the low birefringence. These results indicate that promising materials for high-performance optical applications can be developed based on the well-suited incorporation of the cardo structure into the polymer backbone.