| Abstract
| - A new class of silicon-containing poly(cyanoterephthalylidene) copolymers with a uniformπ-conjugated segment was synthesized using the Knoevenagel reaction between the dialdehyde monomerand the appropriate diacetonitrile. The incorporation of organosilicon units with the flexible alkyl sidegroup into the polymer rigid backbone would afford processable electroluminescent materials and interruptthe regular π-conjugated chains. The resulting polymers were highly soluble in common organic solvents.The Mn and Mw of the resulting polymers are in the range 3800−4200 and 5400−6000 with a polydispersityindex range of 1.38−1.43, respectively. Their glass transition temperature was in the range of 82−87°C. According to the molecular mechanical calculations for single chain models of SiBuPPV andSiBuCNPPV, trans conformations are more stable than cis conformations. The UV−visible absorbanceof present polymers show strong absorption bands around 340−360 nm, since the π-conjugated systemis regulated by organosilicon units. Their photoluminescence spectra appeared around 460−470 nm inthe blue region. The threshold voltage of the SiHMCNPPV was about 7 V. Surprisingly, these polymersexhibit blue light-emitting diodes in the EL emissive band at 480 nm in the blue region, instead of redlight-emitting diodes, when an operating voltage of higher than 7 V is applied. These copolymers showa relatively low operating voltage compared with a block copolymer having well-defined structures becausethe incorporation of electron-withdrawing cyano groups into the π-conjugated system increased the electronaffinity of those polymers and decreased the LUMO energy level.
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