Vinyl carbazole polymerization

There is a cationic analogue of Scheme 11 when TV-vinyl carbazole polymerization was induced by poly(vinyl chloride)-bound dimethylglyoxime complexes of Co11, Ni11, and even Cu11 (Scheme 12).390... 

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 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. 

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. 

Cyclic monomers such as cyclohexene oxide were readily polymerized upon irradiation of the CT complexes of pyridinium salts whereas spontaneous polymerizations were observed upon mixing with strong electron donating monomers such as butyl vinylether and A-vinyl carbazole. These monomers are known to form CT complexes themselves with electron acceptors which may interfere with the rapid polymerization observed. 

When the monomer is attached to the active centre in a manner leading to the formation of a weakly reactive ion, growth is terminated. A typical example of this kind of termination is the formation of an unreactive ion during cationic polymerization of vinyl carbazole. Instead of propagation... 

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. 

Iodine. Iodine successfully initiates or catalyzes polymerization of A-vinyl carbazole, vinyl ethers, and styrenes. It adds to double bonds to form 1,2-diiodosubstituted ethanes which are subsequently ionized in the presence of excess iodine [69,149-151]. Stopped-flow UV studies dem-... 

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. 

Composites of polypyrrole and poly(vinyl chloride) have been prepared by several groups (64-67). Polythiophene-poly(vinyl chloride) composites have also been prepared (68). The electropolymerization of pyrrole on poly(vinyl chloride)-coated electrodes yielded composites with mechanical properties (tensile strength, percent elongation at break, percent elongation at yield) similar to poly(vinyl chloride) (65) but with a conductivity of 5-50 S/cm, which is only slightly inferior to polypyrrole (30-60 S/cm) prepared under similar conditions. In addition, the environmental stability was enhanced. Morphological studies (69) showed that the polypyrrole was not uniformly distributed in the film and had polypyrrole-rich layers next to the electrode. Similarly, poly(vinyl alcohol) (70) poly[(vinylidine chloride)-co-(trifluoroethylene)] (69) and brominated poly(vinyl carbazole) (71) have been used as the matrix polymers. The chemical polymerization of pyrrole in a poly(vinyl alcohol) matrix by ferric chloride and potassium ferricyanide also yielded conducting composites with conductivities of 10 S/cm (72-74). 

Anionic polymerizations of A-ethyl-2-vinyl-carbazole and A-ethyl-3-vinyl-carbazole have also been examined, and the 2-vinyl derivative shown to yield clean living systems. However, the 3-vinyl monomer is very much more reactive and polymerization must be conducted below — 60 °C to get any approximation to a living system. No quantitative information is available. 

Triphenylmethyl halides and tropylium halides ionize to form trityl, (f>3C, and cycloheptatrienyl (tropylium), CyRt", carbocations [Eqs. (P8.20.1) and (P8.20.2)], which are too stable to efficiently polymerize less reactive monomers such as isobutylene and styrene, but polymerization of p-methoxystyrene, vinyl ethers and N-vinyl carbazole, which are more reactive, proceeds rapidly. 

Selenide-Based Nonsalt Photoinitiator In more recent years, diphenyldiselenide (DPDS) as nonsalt initiator was used for photosensitized cationic polymerization of /V-vinyl carbazole (NVC) [69]. Diselenide compounds in the presence of aromatic nitriles are well-known photosensitization system for in situ generation of electrophilic... 

The idea of two simultaneous homo-polymerizations was explored by Szwarc and his co-workers252. Pac and Plesch253 reported initiation of cationic polymerization of vinyl carbazole (VC) by tetranitromethane in nitrobenzene. They postulated the formation of a charge-transfer complex,... 

Reinvestigation of Pleseh s work confirmed their kinetic conclusions, viz. the first order kinetics in monomer, and led to a similar rate constant. However, addition of oxetane to the vinyl-carbazole-tetranitromethane system greatly retarded the vinyl-car-bazole polymerization, e.g. by a factor of 30, but neither the first order character of this reaction nor the molecular weight of the resulting polymer was affected provided that the concentration of oxetane was sufficiently large. At the same time, cationic polymerization of the added oxetane was observed. 

No true living cationic vinyl polymers are known at present, although the papers of Skorokhodov on 1,2-dimethoxyethylene 1011 and of Higashimura on the I2-initiated polymerization of vinyl ethers, p-methoxystyrene (Sect. 15.3.1.1.3) and of N-vinyl carbazole 102) approach living features. It is possible, however, to prepare a vinyl polymer with an end-group that is inactive towards its own monomer but is able to convert a heterocyclic monomer into the onium ion, in this way starting the polymerization of a second monomer. The application of this approach for the synthesis of block copolymers is described below. 

Polymeric nanocomposites are a class of relatively new materials with ample potential applications. Products with commercial applications appeared during the last decade [1], and much industrial and academic interest has been created. Reports on the manufacture of nanocomposites include those made with polyamides [2-5], polyolefins [6-9], polystyrene (PS) and PS copolymers [10, 11], ethylene vinyl alcohol [12-15], acrylics [16-18], polyesters [19, 20], polycarbonate [21, 22], liquid crystalline polymers [8, 23-25], fluoropolymers [26-28], thermoset resins [29-31], polyurethanes [32-37], ethylene-propylene oxide [38], vinyl carbazole [39, 40], polydiacethylene [41], and polyimides (Pis) [42], among others. 

The polymerization of A -vinyl carbazole may be initiated by free radicals, by cations, by organometallic catalysts, by charge-transfer processes, or by electrochemical methods. Since the monomer is a solid at room temperature (m.p. 64-66°C, b.p. 154-155°C/3 mm), solid state polymerizations have been carried out both on powdered monomer and on the surfaces of larger crystals. In this process, the reactive species propagates into the interior of the solid. 

Higashimura et al. [28] studied the solid-state polymerization of V-vinyl-carbazole using various catalysts and determined the molecular weight distribution of the polymer by gel permeation chromatography (GPC). The polymers... 

In a heterogeneous system, powdered biosynthesized y-poly(glutamic acid), in the free acid form, has been used to initiate the polymerization of IV-vinyl-carbazole as well as AT-vinyl-2-pyrrolidone. The rate of polymerization in nitrobenzene was greater than in toluene. In the process, there was no significant grafting onto the surface of the y-poly(glutamic acid). It has been proposed that initiation involves proton addition from the surface of the carboxylic acid to the monomer. The propagation proceeds with carboxylate anions on the surface of a counter ion [60]. 

Poly(vinyl carbazole) is produced by polymerization of vinyl carbazole using free-radial initiation or Ziegler-Natta catalysis. 

As was mentioned above, in 2007, it was shown that SWNT covalently functionalized with a polymer may be obtained by a bulk polymerization [33]. The reaction mechanisms that occur in the polymerization processes can be understood by Raman light scattering and FTIR spectroscopic studies, which prove the functionalization of CNTs both with monomers (e.g. N-vinyl carbazole (VK)) and polymer molecules (e.g. PVK) [33]. 

M. Baibarac, I. Baltog, S. Lefi t, and P. Gomez-Romero, Spectroscopic evidence for the bulk polymerization of N-vinyl carbazole in the presence of single-walled carbon nanotubes. Polymer, 48, 5279-5288 (2007). 

Examples of the different types of living cationic polymerization systems are listed in Table 3. All involve relatively fast initiation and optimal equilibria between a low concentration of active carbenium ions and a high concentration of dormant species (Scheme 9). Only hydroiodic acid initiated polymerizations of A-vinyl carbazol are controlled in the absence of a Lewis acid activator or a nulceophilic deactivator [115]. 

All polymerizations done in boizene with (N-vinyl carbazole] 0.1 [M] in ait. 

Each polymerization carried out using monomer (N>vinyl carbazole) 0.097 g at 55 °C in nitrogen atmosphere in benzene medium. 

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