Polymers carbazole-containing

A series of carbazole-3,6-diyl polymers, including homopolymer 537c, alternating carba-zole-oxadiazole and carbazole-fluorene copolymers 541-545 and analogous random copolymers containing all three (carbazole, fluorene, and oxadiazole) units were prepared and 

As demonstrated in previous sections, the carbazole unit was introduced as a pendant group or as a chain member in major classes of EL polymers such as PPVs (95-105,141,177, 190) and PFs (62, 63, 242-245). A variety of 2,7-carbazole-derived polymers with different conjugated units, such as 2-alkoxy- and 2,5-dialkoxy-l,4-phenylene (549) and l,l -binaphtha-lene-6,6 -diyl (550 [658]), 2,5-pyridine (551), 2,7-fluorene (245 [345,346]), 2,5 -bithiophene (554 [345]), 5,8-quinoxaline (552), quinquethiophene-SjS -dioxide (450 [550]), 2,5-thiophene (553), 2,5-furan (555), and acetylene (556 [659]) were reported by Leclerc and coworkers 

SCHEME 2.73 Synthesis of 2,7-dihalocarbazole monomers and their polymerization by Yamamoto and Suzuki protocols. (From Morin, J.-F. and Leclerc, M., Macromolecules, 34, 4680, 2001 Morin, J.-F. and Leclerc, M., Macromolecules, 35, 8413, 2002 Zotti, G., Schiavon, G., Zecchin, S., Morin, J.-F., and Leclerc, M., Macromolecules, 35, 2122, 2002 Iraqi, A. and Wataru, I., Chem. Mater., 16, 442, 2004.) 

SCHEME 2.74 Synthesis of ladder-type polycarbazole 557. (From Patil, S.A., Scherf, U., and Kadaschuk, A., Adv. Fund. Mater., 13, 609, 2003.) 

Very recently, Leclerc and coworkers [661] synthesized a series of 2,7-carbazolylene-vinylene copolymers 558-561 via Horner-Emmons reaction. Although all the copolymers are fluorescent in solution (APL 460-505 nm, d PL 16-67%), only 559 retains its fluorescence in the solid state (Apl = 656, 701 nm). A device ITO/PEDOT/559/LiF/Al/Ag emitted orange-red light (AEL = 640 nm, CIE 1976 coordinates u = 0.40, V = 0.54) with a low turn-on voltage of 3 V, an efficiency of 0.17 cd/A (at 5 V), and a maximum brightness of 245 cd/m2 (at 10 V) (Chart 2.131). 

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Similar PPV-based copolymers with carbazole and fluorene units in the backbone 101 and 102 (and also similar copolymers with oxadiazole substituents 103 and 104) have been synthesized by Ree and coworkers [148], Much lower PL efficiency in films was found in this case for carbazole-containing polymers 102 and 104 (1-4%), when compared to materials prepared by Shim (95 and 96, 59-64%) (Chart 2.21). 

J.V. Grazulevicius, P. Strohriegl, J. Pielichowski, and K. Pielichowski, Carbazole-containing polymers synthesis, properties and applications, Prog. Polym. Sci., 29 1297-1353, 2003. 

Donor-Acceptor Complexes of Carbazole-Containing Polymers... 

Intrinsically carbazole containing polymers are photosensitive in the UV range of spectra. The applications of such polymers in electrophotography and related processes need sensitization to the visual wavelengths. The most acceptable method is charge transfer formation between polymer donor and acceptor molecules. Hoegl pointed out that 0.1-2% of acceptor molecules inserted in the polymer matrix lead to a substantial increase in the photoconductivity especially in the CT bands. Subsequently, a lot of paper were published for CT-carbazole-containing complexes and such materials were used in photosensitive processes. Various types of molecules were used as a photosensitizers. 

Subsequently, Cao et al. incorpated electron and hole transporting groups on to the zinc(II) Schiff base polymer chain for PLEDs application (Fig. 21).35 Fluorene and carbazole-containing polymers were prepared by reacting the... 

The following photoconductive polymers can also be clarified as polymers of aromatic amines poly(N-vinylphenothiazine) and poly(N-vinylphenoxazine ° and poly(N-acrylodibenzazepine) ° Poly(N-vinylcarbazole) is basically a modified vinyldiphenylamine polymer . It has yet to be detemined if the transport characteristics of PVK with the diphenyl amino group forced into planarity are different from those of poly(N-vinyldiphenylamine) which would possess a greater freedom of rotation. The properties of PVK have been discussed in many articles and reviews [for example see Ref. ]. Several articles and patents have been published recently which deal with carbazole containing polymers other than PVK, and copolymers of N-vinylcarbazole with some other monomers. 

Other carbazole-containing polymers are also photoconductive [2]. Among the carbazole polymers studied in detail are poly(N-epoxy-propylcarbazole) [75], poly[y-08-N-carbazolylethyl)-L-glutamate] [76] and poly[ -(N-carbazolyl vinyl ether)] [77]. Charge mobilities in these polymers are comparable to those in PVK, but they form tougher, less brittle films. 

Essentially there are two major ways in which optical activity may be introduced into synthetic polymers. Most obviously the synthesis and utilization of inherently chiral monomers may be employed. Alternatively, and perhaps more conveniently, a prochiral monomer may be copolymerized with a suitable chiral comonomer. For carbazole-containing polymers both synthetic approaches have been employed. 

From these results, and from the reported extrapolated values of 276 °C (syndiotactic) and 126 °C (isotactic) for the glass transition temperatures of PNVC it has been concluded that rotational eclipsing in isotactic NVC sequences is very much more favourable than in corresponding syndiotactic sequences. This contusion is strongly supported by examination of space filling molecular models. Such considerations must be borne in mind when considering the optical and chiroptical properties of carbazole containing polymers and it has to be expected that copolymers of NVC will have fluorescence emission properties that can be related to both main chain tacticity and distribution of monomeric units. Free radically polymerized mixtures of NVC and acrylic derivatives of (—)-menthol have fluorescence spectra... 

Electronic transitions of the carbazole chromophores afford a highly sensitive probe for studies of carbazole-containing polymers in respect of their absorption and emission characteristics as well as of either inherent or induced circular dichroism. They have been conveniently employed to describe microstructural characteristics of carbazole-containing polymers, including homopolymers of carbazolated a-aminoacids and of vinylated carbazoles with chiral substituents. Data obtained are entirely consistent with interpretation of polymer structures derived from related UV absorption, excimer fluorescence emission and NMR studies and are especially valuable as a completely new indication of copolymer sequence distributions. 

Rather unusually, induced circular dichroism in copolymers of N-vinylcarbazole with different optically active monomers is optimized at particular copolymer compositions and hence offers an obvious route to the design of optically active polymer reagents from N-vinylcarbazole. Analogously, the dependence of excimer emission properties in carbazole-containing polymers on the primary structure of the monomeric units and the microstructure of the polymer backbone offers the possibility to design polymeric systems with predictable photoresponses and energy transfer characteristics. 

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