Synthesis and property modulation of linearly polarized luminescent side-chain polymers with room-temperature phosphorescence

Abstract

Linearly polarized luminescent (LPL) materials have garnered significant interest for their applications in linearly polarized organic light-emitting diodes, displays and so forth. However, the majority of previous reports have mainly focused on linearly polarized fluorescent materials. Linearly polarized phosphorescent materials have been rarely reported mainly because of their unstable triplet excitons and difficulties in orientation control of phosphorescent chromophores. Herein, side-chain polymers PMDFMmC (m = 0, 2, 4, and 6) with room-temperature phosphorescence (RTP) are synthesized. The oriented PMDFMmC films are then prepared by a template-assisted method. By changing the flexible spacer length of PMDFMmC, their photo-physical properties are well regulated. As the flexible spacer length increases, the glass transition temperature (T_g) of polymers decreases from 110 °C to 58 °C, the phosphorescence lifetime decreases from 629.8 ms to 476.8 ms, and the phosphorescence color changes from orange-red to yellow. All oriented PMDFMmC films also show good linearly polarized phosphorescent properties. Meanwhile, as the flexible spacer length increases, the dichroic ratio and polarization ratio values gradually enhance. Using oriented PMDFM6C films, linearly polarized phosphorescence dichroic ratio and polarization ratio values of 14.8 and 0.87, respectively, can be achieved.