N-Vinyl carbazole

Applying these methodologies monomers such as isobutylene, vinyl ethers, styrene and styrenic derivatives, oxazolines, N-vinyl carbazole, etc. can be efficiently polymerized leading to well-defined structures. Compared to anionic polymerization cationic polymerization requires less demanding experimental conditions and can be applied at room temperature or higher in many cases, and a wide variety of monomers with pendant functional groups can be used. Despite the recent developments in cationic polymerization the method cannot be used with the same success for the synthesis of well-defined complex copolymeric architectures. 

The only studies on olefin polymerisations in methylene dichloride in which kp was deduced directly from the rate of reaction were carried out by Ledwith and his collaborators [9, 13] with extremely low concentrations of monomer and catalyst. They polymerised isobutyl vinyl ether and N-vinyl carbazole in a Biddulph-Plesch calorimeter with trityl or tropylium salts and obtained the first-order rate constants k1 from the conversion curves. Since different catalysts gave the same ratio of kx c they concluded that for each of them Xxr = c0 and hence identified with kp which must in fact be k p, as explained above. It seems unlikely that if several initiators give the same value of kp, they do so because they are all equally inefficient, and the inference that they do so because they are all 100% efficient, i.e., that for all of them x = c0, seems plausible - but it would be useful to have a direct check of this. 

The calorimetric method was applied by Bowyer et al. (1971) to the polymerisation of N-vinyl carbazole (NVC) by tropylium hexafluoroantimonate and perchlorate in CH2C12 at 0 °C and -25 °C. The reactions were very fast and the reaction curves had a monotonically decreasing rate from the start. The initial reaction rate, R0, was correlated with the initiator and monomer concentrations by the equation... 

On the methods of analysis of the thermally stimulated current and the values of the trap depth in poly-N-vinyl-carbazole... 

Another useful commercial polymer is poly N-vinyl carbazole which is of interest in reprographic systems due to its photoactive properties. Here there is competition be-... 

There seems no doubt that organic photoconductor systems will permit the development of new reproduction processes based on the electrophotographic principle 10>. Dyes play an important role in this development on the one hand they act as spectral sensitizers of the organic photoconductors (e.g. poly-N-vinyl-carbazole 161> and on the other hand, the photoelectric effects of dyes are important for... 

It is interesting that N-ethyl-3-vinyl carbazole 7 polymerises readily by cationic processes and the value of k estimated by initiation with tropylium ion is 2x 104 M-1 sec-1, approximately one order of magnitude lower than that for the closely related N-vinyl carbazole (159). 

The simplest procedure for grafting copolymerization, in terms of number of components in the reaction medium, is a bulk polymerization of the monomer in mixture with the molten polyamide. This has been claimed in an earlier patent (2), related to improvements in dyeability and hydrophylic properties of the resulting yam, obtained by melt spinning of the product of reaction with monomers such as 2,5-dichloro styrene, lauryl methacrylate, N-vinyl pyrrolidone, and N-vinyl carbazole. 

Polymeric charge transfer complexes of poly(N-vinyl carbazole) and TCNQ have also been investigated 104). These contained relatively little TCNQ <3 mole %). Consequently little enhancement of conductivity was observed. 

Taniguchi, A., S. Kanda, X. Nogaito, S Kusabayashi, H. Mikawa, and I. Ito The electrical properties of poly(N-vinyl carbazole)/TCNQ polymers. Bull. Chem. Soc., Japan 37, 1386 (1964). 

In the first part of this chapter we review some basic concepts of photoconductivity which are followed by a renew of some experimental techniques and how these have been applied to characterize some of the well known polymeric systems such as poly(N-vinyl carbazole) (PVK) and the charge transfer complex of PVK and 2,4,7,trinitro-9-fluorenone (TNF). The second part of this chapter is a review of the extensive original and patent literature on a variety of photoconducting polymers. 

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. 

Acrylonitrile Methacrylamide N-Vinyl carbazole DMF"1 H,0 THF CH,C1, C7H7+CI04 273 K... 

Cationic polymerizations are not only important commercial processes, but, in some cases, are attractive laboratory techniques for preparing well-defined polymers and copolymers. Polyacetal, poly(tetramethyl-ene glycol), poly(e-caprolactam), polyaziridine, polysiloxanes, as well as butyl rubber, poly(N-vinyl carbazol), polyindenes, and poly(vinyl ether)s are synthesized commercially by cationic polymerizations. Some of these important polymers can only be prepared cationically. Living cationic polymerizations recently have been developed in which polymers with controlled molecular weights and narrow polydispersity can be prepared. 

Due to resonance stabilization and their higher nucleophilicity, heteroatoms stabilize the growing carbenium ions better than alkyl and aryl groups do N-vinyl carbazole is more reactive than vinyl ethers because of nitrogen s higher nucleophilicity. However, the reactivity of the growing carbenium ions follows the opposite order shown above, with the most stable... 

Other Lewis Acids. Several relatively weak Lewis acids such as zinc halides and mercury halides initiate polymerization of the most reactive monomers such as N-vinyl carbazole, vinyl ethers, and alkoxysty-renes. Many of these acids have poor solubility in hydrocarbons and halo-genated hydrocarbons and are therefore used as acetone or ether solutions. However, such solvents act as nucleophiles, and therefore decrease the acids Lewis acidity. 

Other monomers that are suitable for cationic polymerization include cyclic ethers (like tetrahydrofuran), cyclic acetals (like irioxane), vinyl ethers, and N-vinyl carbazole. In these cases the hetero atom is bonded directly to the electron deficient carbon atom, and the respective carboxonium ion (9-13) and immonium ion (9-14) arc more stable than the corresponding carbocalions. 

Figure 3. x versus 1/T for hole transport in PVK and poly(3-bromo-N-vinyl-carbazole) (3-Br-PVK), with current-mode transients at the indicated temperatures. The various symbols indicate data taken at various times. (Reproduced with permission from reference 34. Copyright 1978 American Institute of... 

Silicon-Based Polymer Science A Comprehensive Resource POLY (N-VINYL CARBAZOLE)... 

Photolysis of solutions of N-vinyl carbazole (NVQ in the presence of aromatic carbonyl impounds such as benzophenone, anthraquinone, fluorenone, and chloranil leads to efficient cyclodimerisation fS oducing the cyclobutane (VI). 

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