ABSTRACT
Polymers....................................................................... 182 5.2.1 Poly(p-Phenylenevinylene)s (PPVs)................. 182
5.2.1.1 Unsubstituted PPVs ........................... 182 5.2.1.2 Alkyl-and Alkoxy-Substituted
PPVs..................................................... 183 5.2.1.3 PPV Backbone Modifications ............. 187 5.2.1.4 Control of Conjugation Length
in PPVs................................................ 200 5.2.1.5 Oligomer Approach ............................. 201
5.2.2 Poly(Phenyleneethynylene)s (PPEs)................ 204 5.2.3 Poly(p-Phenylene)s (PPPs)............................... 205
5.2.3.1 Substituted PPPs and Copolymers.... 205 5.2.3.2 Copolymers Containing
Oligophenylene and Olefin Units ...... 206
5.2.3.3 Water-Soluble PPPs ............................ 207 5.2.3.4 Ladder-Structure PPPs ...................... 208
5.2.4 Polyfluorenes (PFs)........................................... 210 5.2.4.1 PF Homopolymers............................... 210 5.2.4.2 Strategies to Minimize Excimer
Emission .............................................. 211 5.2.4.3 PF Copolymers .................................... 214
5.2.5 Polythiophenes (PTs)........................................ 218 5.2.6 Conjugated Polymers with Electron-
Deficient Heterocyclic Units ............................ 220 5.2.7 Polymers with Side Chain Chromophores...... 221
5.3 Survey of the Synthetic Chemistry for Electroluminescent Polymers ..................................... 223 5.3.1 Historically Relevant Reactions ...................... 223
5.3.1.1 FeCl3-Catalyzed Condensation Polymerization .................................... 223
5.3.1.2 Friedel-Crafts Polymerization........... 224 5.3.2 Metal-Mediated Polycondensation
Reactions ........................................................... 224 5.3.2.1 Polycondensation of
Organomagnesium Monomers .......... 224 5.3.2.2 The McCullough Method for PTs ...... 225 5.3.2.3 The Rieke Method for PTs ................. 225 5.3.2.4 The Heck Reaction.............................. 226 5.3.2.5 The Suzuki Reaction .......................... 228 5.3.2.6 The Stille Coupling Reaction ............. 233 5.3.2.7 The McMurry Reaction ...................... 234 5.3.2.8 The Sonogashira-Hagihara
Reaction ............................................... 235 5.3.3 Metathesis Polymerization .............................. 236
5.3.3.1 Acyclic Diyne Metathesis Polymerization .................................... 236
5.3.3.2 Ring Opening Olefin Metathesis Polymerization .................................... 238
5.3.4 Wittig and Wittig-Horner Reactions .............. 238 5.3.5 The Knoevenagel Reaction .............................. 241 5.3.6 The Wessling Method ....................................... 242 5.3.7 Dehydrohalogenation Condensation
Polymerization .................................................. 244
5.3.8 Reductive Polymerization ................................ 247 5.3.8.1 Yamamoto-Type Aryl-Aryl
Coupling............................................... 247 5.3.8.2 Ullmann Coupling Reaction............... 248
5.4 Overall Perspective and Future Challenges ............. 248 References............................................................................. 249
5.1 INTRODUCTION
Although organic electroluminescence (EL) was reported in the 1950s,1 it was not until Tang’s report in 1987 that it would be seriously considered of commercial importance. Tang successfully developed organic light-emitting diodes (OLEDs) with a luminance of over 1000 cd/m2 at a voltage of 10 V.2 Interest further intensified with the report of EL from devices based on poly(p-phenylenevinylene) (PPV, 1).3 The manufacturing simplicity of polymer light-emitting diodes (PLEDs) opened the opportunity for LED fabrication by casting the electroluminescent layer from solution.4 With solution methods, one can envision the manufacture of thin, flexible, largearea full-color displays.
