Conjugated chromophores strategy

A major challenge in the last few years remained the development of materials that combine the processability of polymers with the defined optical and electrical properties of low molecular weight chromophores. Strategies to optimize electrooptical and mechanical properties in OLEDs have generally implemented the use of chromophores with defined conjugation length either inserted in the polymer backbone or alternatively... 

The logical continuation of the stepladder strategy outlined above for minimizing the mutual distorsion of adjacent main chain phenylene units was the incorporation of the complete PPP-parent chromophore into the network of a completely planar ladder polymer. The complete flattening of the conjugated 7T-system by bridging of all the subunits should then lead to maximum conjuga-tive interaction. As with the PTHP 11 systems, alkyl or alkoxy side chains should lead to solubilization of the polymers. 

More recently, Marks and coworkers developed a totally different approach for obtaining very high fi values. Their strategy does not focus on extensive planar 7r-conjugation, which is prone to chemical, thermal, and photochemical instabilities [58], but on twisted 7r-electron system chromophores. These unconventional twisted % zwitterionic structures (TM and TMC) exhibit unprecedented hyperpolarizabilities as large as 15 times greater than those reported previously (fj.fi as high as -488,000 x 10 48 esu) [59,60],... 

A useful strategy in the design of new polymeric materials for electronic applications is the incorporation of a chromophore unit into the conjugated backbone of the polymer. One such class of chromophoric compounds that have gained interest over the past decade is represented by diketopyrrolopyrrole (DPP) derivatives. The chromophoric properties are attributed to the intramolecular charge transfer (ICT) between the aryl substituents at the 3- and 6- positions to the electron deficient lactam units. Tieke et al have reported an... 

---