Synergistic effect between carbon black nanoparticles and polyimide on refractive indices of polyimide/carbon black nanocomposites
Abstract
High refractive index polyimide (PI)–chloride modified carbon black hybrid materials were prepared. The introduction of chloride modified CBs endowed the PI/CB nanocomposites with high refractive index, and the effect of the interaction between the five-membered imide rings and aromatic rings of CBs on the high refractive indices and transparency of the resulting PI/CB nanocomposites was discussed. The refractive indices of the prepared hybrid films at 633 nm were in the range of 1.711–1.833, which increased with the CB content from 0 to 10 wt%. According to the comparison of the theoretical and experimental values, the higher refractive index is mainly due to the effective enhancement of intra- and intermolecular charge transfer (CT) interactions between the five-membered imide rings and chlorine atoms attached directly to the CBs and the adjacent benzene rings of CBs. A theoretical equation based on the modified Lorentz–Lorenz theory provided reasonably close estimation of the refractive indices to the experimentally observed values.