Synthesis and Characterization of Fluorene-Based Copolymers Containing Siloxane or Distilbene Moieties on Their Main Chain

Abstract

Two novel types of polyfluorene copolymers containing siloxane linkages or distilbene moieties on their main-chains were synthesized by Ni(0)-mediated Yamamoto coupling polymerization. These polymers, designated P2Silo05, P2Silo15, PF-P02, and PF-P05 were prepared by copolymerization between 2,7-dibromo-9,9'-dihexylfluorene and bis(bromobenzene)-terminated disiloxane monomer (for P2Silo05 and P2Silo15) or dibromodistilbene monomer (for PF-P02 and PF-P05). All of the polymers were highly soluble in common organic solvents such as chloroform, toluene, and p-xylene. The glass transition temperatures of the polymers were between 92 and 113 degrees C, and the decomposition temperatures for a 5% weight loss (T(d)) were above 420 degrees C for all of the polymers, demonstrating high thermal stability. The molecular weight (M(w)) of the polymers ranged from 4.2 x 10(4) to 8.8 x 10(4). The blue shift of the maximum in the UV-visible absorption was greater in polymers with a higher molar percentage of siloxane linkages or distilbene moieties than in homo poly (dihexylfluorene) (PDHF). However, the photoluminescence spectra of the polymers were similar to those of PDHF in terms of the onsets and patterns. Single-layer light-emitting diodes were fabricated with a configuration of ITO/PEDOT:PSS/polymers/Ca/Al. The maximum electroluminescence emission wavelengths of the polymers were 425-450 nm, corresponding to pure blue light. The CIE co-ordinates of the polyfluorenes containing siloxane linkages or distilbene moieties ranged from (0.21, 0.21) to (0.17, 0.10), indicating deeper blue light than that of PDHF {CIE co-ordinates of (0.25, 0.29)}, with P2Silo15 giving the deepest blue-light {CIE co-ordinates of (0.17, 0.10)}. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1595-1608, 2009