Solution polymerization behavior of N‐vinylcarbazole by low‐temperature azoinitiator

N‐Vinylcarbazole (VCZ) was solution polymerized in 1,1,2,2,‐tetrachloroethane (TCE) at 30, 40, and 50°C using a low‐temperature initiator, 2,2'‐azobis(2,4‐dimethylvaleronitrile) (ADMVN); the effects of polymerization temperature and concentrations of initiator and solvent were investigated. On the whole, the experimental results corresponded to predicted ones. Low‐polymerization temperature using ADMVN proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of high molecular weight with smaller temperature rise during polymerization, nevertheless of free radical polymerization by azoinitiator. The polymerization rate of VCZ in TCE was proportional to the 0.46 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in TCE at 30°C using ADMVN concentration of 0.00005 mol/mol of VCZ, weight‐average molecular weight of 271 000 was obtained, with polydispersity index of 1.66. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1558–1563, 2000     

Preparation of high molecular weight poly(N‐vinylcarbazole) in high yield by low‐temperature precipitation polymerization of N‐vinylcarbazole

To produce high molecular weight poly(N‐vinylcarbazole) (PVCZ) with high conversion, N‐vinylcarbazole (VCZ) was heterogeneously polymerized in methanol at 30, 40 and 50 °C using a low temperature initiator, 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN), and the effects of polymerization temperature and concentration of initiator and solvent on the polymerization behaviour and molecular parameters of PVCZ investigated. Globally, experimental results correspond to predicted ones. Low polymerization temperature using ADMVN and a heterogeneous system using methanol proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of high molecular weight and high conversion with small temperature rise during polymerization, although free radical polymerization by azoinitiator was used. The polymerization rate of VCZ in methanol at 30 °C is proportional to the 0.88th power of ADMVN concentration. The molecular weight is higher and the molecular weight distribution is narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in methanol at 30 °C using an ADMVN concentration of 0.0001 mol/mol of VCZ, a weight average molecular weight of 1 750 000 g mol⁻¹ is obtained, with a polydispersity index of 1.82 © 2000 Society of Chemical Industry     

Preparation of high‐molecular‐weight poly(N‐vinylcarbazole) by the photoinduced low‐temperature solution polymerization of N‐vinylcarbazole in 1,1,2,2‐tetrachloroethane

For the preparation of high‐molecular‐weight (HMW) poly(N‐vinylcarbazole) (PVCZ) with a narrow molecular weight distribution, N‐vinylcarbazole (VCZ) was solution‐polymerized in 1,1,2,2‐tetrachloroethane (TCE) at ?20, 0, and 20°C with photoinitiation. The effects of the polymerization temperature and the concentrations of the polymerization solvent and photoinitiator on the polymerization behavior and molecular parameters of PVCZ were investigated. A low polymerization temperature with photoirradiation was successful in obtaining HMW PVCZ with a smaller temperature rise during polymerization than that for thermal free‐radical polymerization by azobisisobutyronitrile (AIBN). The photo‐solution‐polymerization rate of VCZ in TCE was proportional to [AIBN]^0.45. The molecular weight was higher and the molecular weight distribution was narrower for PVCZ made at lower temperatures. For PVCZ prepared in TCE at ?20°C with a photoinitiator concentration of 0.00003 mol/mol of VCZ, a weight‐average molecular weight of 920,000 was obtained, with a polydispersity index of 1.46, and the degree of transparency converged to about 99%. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2391–2396, 2003     

Oxidative polymerization of N‐vinylcarbazole in polymer matrix

A new class of soluble conductive poly(N‐vinylcarbazole) (PVCz) compounds has been developed by oxidative matrix polymerization of N‐vinylcarbazole (NVCz) by Ce(IV) in the presence of poly(ethylene glycol) (PEG). PEG was found to be a more suitable matrix with which to obtain a stable homogenous ternary complex solution when compared with poly(acrylic acid) (PAA) and poly(vinylpyrrolidone) (PVP). The role of PEG, NVCz and Ce(IV) concentration, order of component addition, the structure of the polymer matrix, molecular weight of polymer and the effect of solvent have been investigated. Obtaining soluble PEG–Ce(III)–PVCz ternary complexes was shown by cyclic voltammetric measurements, and the initial rate of formation NVCz cation radicals as calculated using UV–visible spectrophotometry. Advantageously with these soluble complexes, conductivities could be measured both in solution and in the solid state. © 2001 Society of Chemical Industry     

Photophysical studies of copolymers of N‐vinylcarbazole

The absorption, fluorescence excitation and emission spectroscopy, and time‐dependent spectrofluorimetry have been used to study the photophysics of copolymers of N‐vinylcarbazole with different monomers like vinyl acetate, methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate in dichloromethane. In all the copolymers and at different N‐vinylcarbazole content, the absorption spectra reflect only the monomer carbazole units. The two kinds of excited monomer species of N‐vinylcarbazole are present in S₁ state. Short‐lived (～3 ns) excited monomer decays forming low energy excimer obtained by the complete overlap of the excited carbazole monomer. The long‐lived excited monomer (～8 ns) decays to ground state without formation of any excimer. The high energy excimer is relatively short‐lived and is formed by the partial overlap of the carbazole units. The presence of bulky group in the copolymer chain hinders the formation of excimers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 372–380, 2006     

Polymerization of N‐vinylcarbazole by multiwalled carbon nanotube

N‐vinylcarbazole (NVC) was polymerized in bulk or in toluene in presence of multiwalled carbon nanotube (MWCNT) without any extraneous catalyst. The formation of polyN‐vinylcarbazole (PNVC) was endorsed by striking agreement of FTIR, fluorescence and UV‐visible spectroscopic, thermogravimetric stability, differential scanning calorimetry, and dielectric characteristics of this polymer with the corresponding literature data for authentic PNVC samples prepared by free radical or carbocationic initiation. The polymerization was supposed to be initiated by a single electron transfer between N lone pair of NVC and the electron deficient MWCNT moieties. While PNVC homopolymer is nonconducting (10^?12 to 10^?16 S/cm), a composite of PNVC with MWCNT isolated from the polymerization system showed high dc conductivity varying from 1.3 to 33 S/cm depending upon the extent of MWCNT loading in the composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4121–4126, 2007     

One‐step,one‐pot photoinitiation of free radical and free radical promoted cationic polymerizations

We describe here a novel approach to photoinitiate free radical and cationic polymerizations concurrently, involving the use of benzoin in conjunction with an onium salt such as diphenyl iodonium or N‐alkoxy pyridinium salt. On photolysis, benzoyl radicals formed from the decomposition of benzoin initiate free radical polymerization of methyl methacrylate. The hydroxy benzyl radicals formed concomitantly are readily oxidized to the corresponding cation by the onium salt to initiate cationic polymerization of cyclohexene oxide in the same system. Evidence for two independent polymerizations was obtained from studies involving gel permeation chromatography, extractions, and infrared and proton nuclear magnetic resonance analysis of the polymers. The effect of the type of the onium salt on each polymerization was also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2389–2395, 2002     

Poly(N‐vinylcarbazole)–clay nanocomposite materials prepared by photoinitiated polymerization with triarylsulfonium salt initiator

A series of polymer–clay nanocomposite (PCN) materials that consist of poly(N‐vinylcarbazole) (PNVC) and layered montmorillonite (MMT) clay are prepared by effectively dispersing the inorganic nanolayers of MMT in an organic PNVC matrix via in situ photoinitiated polymerization with triarylsulfonium salt as the initiator. Organic NVC monomers are first intercalated into the interlayer regions of the organophilic clay hosts, followed by one‐step UV‐radiation polymerization. The as‐synthesized PCN materials are typically characterized by Fourier transform IR spectroscopy, wide‐angle X‐ray diffraction, and transmission electron microscopy. The molecular weights of PNVCs extracted from the PCN materials and the bulk PNVC are determined by gel permeation chromatography analysis with tetrahydrofuran as the eluant. The morphological image of the synthesized materials is observed by an optical polarizing microscope. The effects of the material composition on the optical properties and thermal stability of PNVCs and a series of PCN materials (solution and fine powder) are also studied by UV–visible absorption spectra measurements, thermogravimetric analysis, and differential scanning calorimetry, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1904–1912, 2004     

Ultrasonic study of molecular association of poly(vinyl chloride) solution in tetrahydrofuran

Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules.     

Nuclear magnetic resonance studies of N‐vinylcarbazole/methyl methacrylate copolymers

Copolymers of N‐vinylcarbazole and methyl methacrylate of different compositions were prepared by solution polymerization with azobisisobutyronitrile as an initiator, and their compositions were determined from quantitative ¹³C{¹H}‐NMR spectroscopy. The reactivity ratios for the comonomers were calculated with the Kelen–Tudos and nonlinear error‐in‐variable methods. The complete spectral assignment of the overlapping ¹H and ¹³C{¹H} spectra of the copolymers was made with the help of distortionless enhancement by polarization transfer, two‐dimensional heteronuclear single‐quantum correlation, and total correlation spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3005–3012, 2003     

A nanocomposite of poly(N‐vinylcarbazole) with nanodimensional alumina

A nanocomposite of poly(N‐vinylcarbazole) (PNVC) and Al₂O₃ was prepared by precipitation of a preformed PNVC in a tetrahydrofuran solution onto an aqueous suspension of nanodimensional Al₂O₃. Prolonged extraction of a PNVC–Al₂O₃ composite by benzene failed to extract the loaded PNVC from the Al₂O₃, as shown by Fourier transform infrared studies. Scanning electron microscopy analyses revealed distinct morphological features of the composite, and transmission electron microscopy analyses confirmed that the particle sizes were in the range of 120–240 nm. Thermogravimetric analyses demonstrated the enhanced stability of the nanocomposite relative to the base polymer. Direct current conductivity of the PNVC–Al₂O₃ composites was found to be about 0.14 × 10^?6 S/cm. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2233–2237, 2003     

A water‐dispersible conducting nanocomposite from suspension polymerisation of thiophene in presence of N‐vinylcarbazole

The polymerisation of a mixture of thiophene and N‐vinylcarbazole was achieved in aqueous suspension in the presence of nanodimensional alumina and FeCl₃ as oxidant. The resultant composite was found to contain both polythiophene (PTP) and poly(N‐vinylcarbazole) (PNVC) components even after reflux in benzene, which would remove any PNVC homopolymer. The presence of the individual polymer components was endorsed by FTIR spectroscopic analyses. Thermogravimetric analyses showed that the overall stabilities of the composite and the corresponding homopolymers were in the order: PTP–Al₂O₃ > PTP > PTP–PNVC–Al₂O₃ > PNVC. Differential thermal analyses studies showed the manifestation of two different exotherms corresponding to the presence of two different polymeric constituents in the PTP–PNVC–Al₂O₃ composite. Differential scanning calorimetry studies revealed two glass‐transition temperatures (T_g) suggesting the presence of two polymeric moieties in the PTP–PNVC composite. Scanning electron micrographs of the PTP–Al₂O₃ and PTP–PNVC–Al₂O₃ composites showed distinctive morphological patterns. Transmission electron microscopic images of the composite revealed that the average particle size varied between 20 and 80 nm. DC conductivities of the composites were of the order of 10^?6 S cm^?1. Copyright © 2003 Society of Chemical Industry     

Independent control of lower critical solution temperature and swelling behavior with pH for poly(N‐isopropylacrylamide‐co‐maleic acid)

Polymer solutions that gel in response to changes in temperature and pH are of interest for various forms of drug delivery, and it is desirable to increase swelling for diffusion‐controlled release without bringing the lower critical solution temperature (LCST) above 37°C. N‐isopropylacrylamide (NIP) was polymerized with maleic acid (MAc), a diprotic acid, and acrylic acid (AAc), a monoprotic acid, to compare swelling and temperature response with changes in pH. For samples with equal acid contents and almost identical LCST responses to pH, poly(N‐isopropylacrylamide‐co‐maleic acid) (pNIP MAc) demonstrated greater swelling than poly(N‐isopropylacrylamide‐co‐acrylic acid) (pNIP AAc). The LCST increase for MAc occurred at a pH corresponding to the deprotonation of almost all of the first acid groups. Further increases in pH led to the deprotonation of the second ? COOH and only served to increase the charge concentration at a given location. These results provide strong support for the theory that LCST results largely from uninterrupted chain lengths of NIP and that swelling results from the actual charge density of acid groups along the chain. Because the use of a diprotic acid copolymer allows swelling to be decoupled from LCST, pNIP MAc may be an appropriate candidate for pH‐sensitive drug‐delivery applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2110–2116, 2004     

Microfabrication by X‐ray‐induced polymerization above the lower critical solution temperature

A polymer synthesis method is presented in which chain growth driven by exothermic reaction stimulates a gradual chain collapse. The globular precipitates in such systems can be restrained from coalescing by polymerizing in a quiescent environment. Time‐resolved small‐angle scattering study of the methacrylic acid polymerization kinetics in a quiescent system above its lower critical solution temperature (LCST) in water reveals the following features of this method: (a) growing oligomers remain as rigid chains until a critical chain length is reached, at which they undergo chain collapse, (b) radius of gyration increases linearly with time until a critical conversion is reached, and (c) radius of gyration remains constant after the critical conversion, even while conversion is gradually increasing. Following this self‐stabilizing growth mechanism, we show that nanoparticles can be directly synthesized by polymerizing N‐isopropylacrylamide above its LCST in water. The average size of nanoparticles obtained from a polymer–solvent system is expected to be the maximum extent of reaction spread at that monomer concentration. This hypothesis was then verified by polymerizing N‐isopropylacrylamide above their LCST in water, but by initiating the reaction with X‐rays shielded by a mask. The microfabricated patterns conform well to the size and shape of the mask used confirming that the growing chains do not propagate beyond the exposed regions as long as the reaction temperature is maintained above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 429–425, 2006     

Fabrication and transport properties of poly(N‐vinylcarbazole)‐cellulose triacetate Langmuir‐Schaefer films

Cellulose triacetate (CTA) was doped with poly(N‐vinylcarbazole) during the oxidative polymerization of N‐vinylcarbazole using ferric chloride as an initiator to form polymer blends. The blends were characterized by Fourier transform infrared and UV‐vis spectroscopy. The surface morphology was further studied using both scanning electron microscopy and transmission electron microscopy. Langmuir‐Schaefer films of the polymer blends were fabricated. The DC conductivity of the polymer films at room temperature was found to increase with an increase in CTA content up to a value of 0.001 S cm⁻¹. The temperature‐dependent DC conductivity of the polymer films studied in the range of 300–500 K shows an increase in conductivity with an increase in temperature indicating a semiconducting behavior with a negative temperature coefficient of resistivity. The apparent activation energy also showed a pronounced effect with an increase in the temperature as well as an increase in the content of CTA. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Conducting composites of poly(N‐vinylcarbazole), polypyrrole,and polyaniline with 13X‐zeolite

N‐vinylcarbazole (NVC) was polymerized by 13X zeolite alone in melt (65°C) or in toluene (110°C) and a poly(N‐vinylcarbazole) (PNVC)‐13X composite was isolated. Composites of polypyrrole (PPY) and polyaniline(PANI) with 13X zeolite were prepared via polymerization of the respective monomers in the presence of dispersion of 13X zeolite in water (CuCl₂ oxidant) and in CHCl₃ (FeCl₃ oxidant) at an ambient temperature. The composites were characterized by Fourier transform infrared analyses. Scanning electron microscopic analyses of various composites indicated the formation of lumpy aggregates of irregular sizes distinct from the morphology of unmodified 13X zeolite. X‐ray diffraction analysis revealed some typical differences between the various composites, depending upon the nature of the polymer incorporated. Thermogravimetric analyses revealed the stability order as: 13X‐zeolite > polymer‐13X‐zeolite > polymer. PNVC‐13X composite was essentially a nonconductor, while PPY‐13X and PANI‐13X composites showed direct current conductivity in the order of 10^?4 S/cm in either system. However, the conductivity of PNVC‐ 13X composite could be improved to 10^?5 and 10^?6 S/cm by loading PPY and PANI, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 913–921, 2006     

A conducting nanocomposite of acetylene black with preformed poly‐N‐vinylcarbazole crosslinked by anhydrous FeCl3

A conducting nanocomposite of crosslinked poly‐N‐vinylcarbazole (CLPNVC) with nanodimensional acetylene black (AB) was prepared by oxidative crosslinking of preformed PNVC through pendant carbazole moieties in presence of anhydrous FeCl₃ as an oxidant and AB suspension in CHCl₃ medium at 65°C. The incorporation of CLPNVC moieties in the CLPNVC‐AB composite was endorsed by Fourier transform infrared analysis. Scanning electron microscopic analysis showed formation of lumpy aggregates with average sizes in the 130–330 nm ranges. The thermal stability of the CLPNVC‐AB composite was appreciably higher than that of the PNVC‐AB composite. The direct current conductivities of the composites were significantly enhanced relative to that of the PNVC homopolymer (10^?12–10^?16 S/cm) and varied in the range of 10^?4–10^?2 S/cm depending on the amount of AB loading in the CLPNVC‐AB composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 819–824, 2006     

Synthesis and electrochemical polymerization of N‐ethylcarbazole‐bis‐3,4‐etyhlenedioxythiophene‐N‐ethylcarbazole comonomer

A new comonomer ECz‐BEDOT‐ECz (EBEE) [ECz: N‐ethylcarbazole‐BEDOT:2,2′‐bis(3,4‐ethyhlenedioxy) thiophene] has been synthesized, characterized, and electropolymerized on Pt and carbon fiber microelectrodes (CFME). The ECz side group of the comonomer plays an important role in determining its physical properties PEBEE and it resembles the behavior of corresponding homopolymer (PECz). PBEDOT was increased by the incorporation of ECz monomer into structure. The environmental stability of PBEDOT was increased by incorporating the ECz unit into the structure. The new comonomer seems prefer to be electrodeposited onto CFME as opposed to Pt. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 795–801, 2007     

Plasma‐induced,solid‐state polymerization of N‐isopropylacrylamide

The radio‐frequency plasma‐initiated polymerization of N‐isopropylacrylamide (NIPAM) in the solid state was performed. The isolated linear polymer was characterized by ¹³C‐NMR, ¹H‐NMR, and Fourier transform infrared spectroscopy, and the effects of selected operational plasma parameters (discharge power and time) on the conversion rates were studied. Reversible transitions at the volume‐phase‐transition temperatures of the swelled poly(N‐isopropylacrylamide) hydrogels were investigated by differential scanning calorimetry. The surface morphologies before and after plasma treatment were followed by scanning electron microscopy. With the obtained X‐ray diffraction results, we propose a solid‐state plasma polymerization mechanism for the NIPAM. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010