Polymers with carbazole structure

Fig. 2. Molecular structures of selected photoconductive polymers with pendent groups (1) poly(A/-vinylcarba2ole) [25067-59-8] (PVK), (2) A/-polysiloxane carbazole, (3) bisphenol A polycarbonate [24936-68-3] (4) polystyrene [9003-53-6] (5) polyvin5i(l,2-/n7 j -bis(9H-carba2ol-9-yl)cyclobutane) [80218-52-6]...

In general, the polymers with polyconjugated systems of double and triple bonds are photoeonductive in the UV and at least part of the visible range. In some cases the photoresponse extends to the near infrared range. Although their usefulness in practical applications has been many times suggested, the results have been more or less disappointing. The main problems still remain difficult synthesis, in most cases poorly identified structure, and with few exceptions insolubility and intractability of the polymers. The direct comparison with poly(N-vinyl carbazole) and other photoeonductive polymers is not possible for lack of comparative data. 

PBD may exhibit short operating lifetimes due to recrystallization or aggregate formation. This leads to phase separation and formation of charge carrier traps that inhibit the desired emission. Therefore, it has been proposed to bond the PBD electron transporting structure to a polymer chain, which results in amorphous materials. For example, poly(methyl methacrylatejs with oxadiazole side chains have been reported [71]. The oxadiazole group may be part of the polymeric backbone, together with carbazole moieties or pheny-lene vinylene moieties [25,26]. 

SCHEME 5.6 Structures of related polyarylene-type ladder polymers with main chain thiophene, carbazole, naphthalene, and anthracene units [32-35]. 

Optically active polymers containing carbazole groups may be synthesised by polymerisation of intrinsically optically active carhazole-containing monomers or by copolymerisation of a variety of optically active co-monomers with nonchiral carbazole-containing monomers. Full details are given and it is concluded that the second method is most useful, not least because it permits a wider variation in polymer backbone structures. V. V. absorption fluorescence emission, NMR, and circular dickroism spectra are reported in detail and help to establish a correlation between photophysical behaviour widi both primary and secondary structural features of the polymers. 

Polymers interesting from the points of view of both non-linear optics and photoconductivity have been prepared by Wada and co-workers [223,224]. They have synthesized a series of head-to-tail polymers with dipolar carbazole chromophores [223]. The structures... 

Transition metal ions, electronically coupled to the conjugated backbone, allowed further tuning of the polymer s redox properties, which behaved complementary to FEDOT. A-B-type polymers with EDOT and carbazole structural units turned out to be another class of polymers anodically coloring that can successfully be combined with alkylenedioxythiophenes. - ... 

Later, Yang and coworkers [84] reported similar electrophosphorescent fluorene copolymers 71 and 72, where the hole-transporting carbazole units have been introduced in the polymer backbone (Chart 4.25). Optimizing the polymer structure (comonomer ratio) and the device structure (blending with electron-transporting material PBD 8), the EQE of 4.9% has been achieved. 

This section highlights the most significant applications of pyrroles, indoles, and carbazoles in the areas covered in CHEC-II(1996) <1996CHEC-II(2)207> and in related fields where substantial advances have been made since 1995. While sections on polymers, dyes, drugs, and medicinal compounds deal with novel applications of both old and new compounds, the survey of natural products has been restricted to those new structures that have been discovered during the past decade. 

Jt OLYSILOXANES WITH PENDANT SIDE CHAINS are interesting materials from both the theoretical and practical points of view. A number of polysiloxanes with various side chains, such as liquid crystals (i, 2), carbazole groups (3), electron-donor and electron-acceptor groups (4), polystyrene (5), and functional groups (hydroxyl or carboxyl) (6), have been synthesized. Polysiloxanes are known for their useful properties, which include flexibility, heat resistance, water repellence, and biological inertness. These properties, combined with the ease with which a tailored polymer structure can be prepared,... 

---