Jt-conjugated polymers

As utilized in the synthesis of PPV-based polymers, soluble precursor routes have been developed for the synthesis of various heterocyclic Jt-conjugated polymers. The two most widely employed of these methods for heterocycle formation, shown in Scheme 66, center around ring closure of pre-polymers containing diacetylene 65 or 1,4-diketone units 66 [335-339]. The synthesis of heterocyclic structures from 1,4-diketones has been a known transformation in organic chemistry for decades. While once mainly used for monomer preparation through various cyclizations, it is now being employed to make heterocycle-containing polymers and copolymers [340-342]. 

Keywords Chain-growth polymerization Condensation polymers Cyclic polymers jt-Conjugated polymers Polycondensation... 

Scheme 8 shows the synthetic routes of the oxadiazole unit containing phospho-nium salt monomers and Scheme 9 outlines the preparation of Jt-conjugated polymers composed of oxadiazole units [67]. The synthetic pathways to the para-linked salt monomer (A) and meta-linked salt monomer (B) are of multisteps, but the synthetic method for each step is not difficult and the product yields of intermediate compounds are very high (75-95%). Treatment of bis(4-methylphenyl)hydrazine with POCl3 results in the formation of the 2,5-bis(4-methylphenyl)-1,3,4-oxadiazole. 

Scheme 11.1 Classification of conductive/ electroactive solids and films, (a) Molecular charge-transfer (CT) complexes and jt-conjugated linear oligomers (b) Mixed electronic-ionic conductors inorganic jt-conjugated polymers and polymer-like...

Figure 11.1 Electronic band diagrams of a nondegenerate Jt-conjugated polymer related to different doping levels, (a) Undoped (neutral state) (b) Slightly doped polymer with localized polaronic levels (c) Moderately doped polymer with polaronic bands (d) Heavily doped polymer with bipolaronic bands. The benzenoid (e) and...

The photophysics of jt-conjugated polymers are reviewed in detail in other chapters of this book. (See, for example, Chapter 3.) Here, we focus on the electronic and photophysical phenomena that occur at the heterojunction between two different semiconductor polymers. The heteroj unctions are formed by combining four different polyfluorene copolymers in blend or bilayer thin films and are investigated using time-resolved and steady-state, temperature- and elec-tric-field-dependent photoluminescence measurements as well as electroluminescence and time-resolved spectroscopy. We review a body of work carried out in our laboratories over the last few years, and published in numerous journal articles (see refs. [13-17]). 

Electroluminescence from Jt-conjugated polymers was first reported in 1990 by Burroughes et al. [1], Compared to inorganic materials and small molecules, polymers promise easy fabrication of large-area displays and illumination devices. In fact, the first flexible polymer light-emitting diode (LED) was demonstrated by Gustafsson et al. in 1992 [2]. 

Kasai, H. et al., STM observation of single molecular chains of Jt-conjugated polymers, Chem. Lett. 7, 696-697, 2002. 

Scheme 1 Synthesis of jt-conjugated polymer incorporated with rhenium(1) 2,2 -bipyridine units. The values of x and y varied from 0 to 0.5 and 1 to 0.5, respectively...

JT-Conjugated Polymers Bearing Electronic and Optical Functionalities. Preparation by Organometallic Polycondensations, Properties and Their Application... 

The main drawback of the PLED device with jt-conjugated polymers is that there is an imbalance between the rate of electrons and hole injection near the interface between the polymer and the cathode. Many approaches have been proposed to improve the performance of the devices such as using... 

Wohlgenannt, M., Tandon, K., Mazumdar, S., Ramasesha, S., and Vardeny, Z. V. 2001. Formation cross-sections of singlet and triplet excitons in Jt-conjugated polymers. Nature 409 494. 

M.S.A. Abdou and S. Holdcroft, Oxidation of jt-conjugated polymers with gold trichloride enhanced stability of the electronically conducting state and electroless deposition of Au°, Synth. Met., 60, 93 96 (1993). 

Figure 8.13. Phototactic transport of functional materials (dye, jt-conjugated polymer, and nanocrystal) by conveyance actions. See color insert.

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