Tunable Photoluminescence of Poly(quinoline)s in Polymer Blend Films and Silica

Abstract

Poly(2,6-[4-plenylquinoline]), PPQ, and poly(2,6-[p-phenylene]-4-phenylquinoline), PPPQ, were synthesized and their photoluminescence was investigated in solution and in different host materials: blends and composites. The polymers form aggregates/excimers in concentrated solutions and gradually dissociate upon dilution. When PPQ were blended with poly(acrylic acid), three different emission peaks at 460, 563, and 605 nm were obtained with increasing poly(acrylic acid) concentration, resulted from the protonation capability and steric hindrance effect of poly(acrylic acid). A sol-gel process was employed to incorporate different concentrations of quinoline polymers into silica. At high polymer concentrations, multiple aggregates were formed within the silica network, leading to the emission of red light. At low polymer concentrations, the polymer chains are isolated and trapped individually in the silica channels, resulting in the emission of blue light. For concentrations in between, moderate interchain interaction leads to the emission of green, yellow and orange colors. These results demonstrate that color tunability can be achieved by simply varying the concentration of quinoline polymers in host materials.