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     

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     

Preparation and evaluation of composites from montmorillonite and some heterocyclic polymers. II. A nanocomposite from N‐vinylcarbazole and ferric chloride‐impregnated montmorillonite polymerization system

The polymerization of N‐vinylcarbazole in the presence of FeCl₃‐impregnated montmorillonite resulted in the formation of a poly(N‐vinylcarbazole)–montmorillonite composite. XRD analysis of the composite revealed no expansion for d₀₀₁ spacing, in sharp contrast to that for the same composite prepared in the absence of FeCl₃. This indicated that the poly(N‐vinylcarbazole) was not intercalated in the montmorillonite lamellae but was glued to it in the same way as was polypyrrole in colloidal silica, zirconia, or tin oxide nanocomposite systems. TEM analysis revealed the particle size of the composite to be in the range 30–40 nm. The dc conductivity of the poly(N‐vinylcarbazole)–montmorillonite composite was in the range (3–5) × 10⁻⁵ S/cm depending upon the FeCl₃ loading of montmorillonite. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2971–2976, 1999     

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 dielectric properties of poly(methyl methacrylate)–clay nanocomposite materials

Poly(methyl methacrylate) (PMMA)–clay nanocomposite (PCN) materials were synthesized through in situ intercalative polymerization. A cationic surfactant, [2(dimethylamino)ethyl]triphenylphosphonium bromide, was used as an intercalating agent with pristine Na⁺‐montmorillonite (MMT). The synthesized PCN materials were subsequently investigated by a series of characterization techniques, including wide‐angle powder X‐ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Compared to pure PMMA, the PCN materials exhibit higher thermal degradation temperatures and glass‐transition temperatures. The dielectric properties of PCN blending with a commercial PMMA material in film form with clay loading from 0.5 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 35–100°C. Significantly depressed dielectric constants and losses were observed for these PCN‐blending materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2175–2181, 2005     

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     

Effect of clay on the properties of poly(styrene‐co‐acrylonitrile)–clay nanocomposites

Clay‐dispersed poly(styrene‐co‐acrylonitrile) nanocomposites (PSAN) were synthesized by a free radical polymerization process. The montmorillonite (MMT) was modified by a cationic surfactant hexadecyltrimethylammonium chloride. The structures of PSAN were determined by wide‐angle X‐ray diffraction and FTIR spectroscopy. The dispersion of silicate layers in the polymer matrix was also revealed by transmission electron microscopy (TEM). It was confirmed that the clay was intercalated and exfoliated in the PSAN matrix. The increased thermal stability of PSAN with the addition of clay was observed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dielectric properties of PSAN were measured in the frequency range 100 Hz to 1 MHz at 35–70°C. It was found that the dielectric constant from the dipole orientation had been suppressed due to the intercalation of clay. The dielectric loss is strongly related to the residual sodium content of clay, which increases as the sodium content increases by the addition of clay. Copyright © 2004 Society of Chemical Industry     

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     

Poly(butylene terephthalate)–clay nanocomposites prepared by melt intercalation: morphology and thermomechanical properties

Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (η_inh), were used for this study (η_inh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry     

A conducting composite based on poly(N‐vinylcarbazole)–formalin resin and acetylene black

A poly(N‐vinylcarbazole) (PNVC)–formalin (FO) resin (PNVC‐FO) was prepared via copolycondensation between N‐vinylcarbazole (NVC) and FO in the presence of dry HCl gas in toluene medium at 110°C. A highly conducting composite of PNVC‐FO resin with nanodimensional acetylene black (AB) was prepared by carrying out the polycondensation reaction in presence of a suspension of acetylene black (AB) in toluene. The inclusion of PNVC in the PNVC‐FO‐AB composite was confirmed by FT‐IR analysis. Scanning electron microscopic analyses of PNVC‐FO resin and PNVC‐FO‐AB composite revealed formation of spherical particles and aggregates of irregular shapes respectively. Thermogravimetric analyses revealed the overall stability order as: AB > PNVC‐FO‐AB composite > PNVC‐FO resin > PNVC homopolymer. In sharp contrast to PNVC and PNVC‐FO resin, which were both nonconducting (10^?12 to 10^?16 S/cm), the conductivity of the composites reached values between 0.75 S/cm and 6.54 S/cm corresponding to AB loading of 28–49 wt % respectively. Temperature versus conductivity studies revealed an initial increase in conductivity upto 200°C and current–voltage characteristics of the PNVC‐FO‐AB composite showed a linear trend consistent with Ohmic behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3837–3843, 2007     

Synthesis of Co3O4/Poly(N‐vinylcarbazole) Core/Shell Composite With Enhanced Optical Property

Co₃O₄/poly(N‐vinylcarbazole) (PNVC) composite with enhanced optical property was synthesized via a simple in situ bulk polymerization of NVC monomers in the presence of Co₃O₄ nanoparticles at an elevated temperature. High‐resolution electron microscopic observations showed that the Co₃O₄ nanoparticles were coated with uniform nanolayer shells of PNVC. Fourier‐transform infrared (FT‐IR) spectroscopy revealed the presence of strong interactions between the PNVC polymer chains with the Co₃O₄ surface in the Co₃O₄/PNVC composite. Raman spectroscopic results supported conclusions based on electron microscopy and FT‐IR spectra. The uniform nanolayer coating of PNVC decreases the inherent bulk conductivity of Co₃O₄, however, significantly increases the fluorescence property of Co₃O₄ nanoparticles.

     

Structure and properties of poly(o‐methoxyaniline)–clay nanocomposite materials

In this study, we prepared a series of polymer–clay nanocomposite (PCN) materials that consisted of an emeraldine base of poly(o‐methoxyaniline) and layered montmorillonite. Organic o‐methoxyaniline monomers were first intercalated into the interlayer regions of organophilic clay hosts followed by a one‐step in situ oxidative polymerization. The as‐synthesized PCN materials were subsequently characterized by FTIR spectroscopy, wide‐angle powder X‐ray diffraction, and transmission electron microscopy. The molecular weights of PMA extracted from PCN materials and bulk PMA were determined by GPC with THF as eluant. Effects of the material composition on the thermal stability, flame resistance, electrical conductivity, and corrosion inhibition performance of PMA, along with a series of PCN materials in the form of fine powder and coating, were also studied by TGA, limiting oxygen index measurements, four‐point probe technique, and electrochemical corrosion measurements, respectively. Morphological images of as‐synthesized materials were also investigated by SEM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1072–1080, 2003     

Thermoresponsive poly(ϵ‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) graft copolymers prepared by a combination of ring‐opening polymerization and sequential azide–alkyne click chemistry

A straightforward strategy is described to synthesize poly(?‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) (PCL‐g‐PNIPAAm) amphiphilic graft copolymers consisting of potentially biodegradable polyester backbones and thermoresponsive grafting chains. PCL with pendent chlorides was prepared by ring‐opening polymerization, followed by conversion of the pendent chlorides to azides. Alkyne‐terminated PNIPAAm was synthesized by atom transfer radial polymerization. Then, the alkyne end‐functionalized PNIPAAm was grafted onto the PCL backbone by a copper‐catalyzed azide–alkyne cycloaddition. PCL‐g‐PNIPAAm graft copolymers self‐assembled into spherical micelles comprised of PCL cores and PNIPAAm coronas. The critical micelle concentrations of the graft copolymers were in the range 7.8–18.2 mg L^?1, depending on copolymer composition. Mean hydrodynamic diameters of micelles were in the range 65–135 nm, which increased as the length of grafting chains grew. PCL‐g‐PNIPAAm micelles were thermosensitive and aggregated upon heating. © 2014 Society of Chemical Industry     

Dehydration of water–alcohol mixtures by vapor permeation through PVA/clay nanocomposite membrane

An organic/inorganic hybrid nanocomposite membrane, poly(vinyl alcohol)/clay (PVAC), was prepared. The morphology of PVAC nanocomposite membranes were characterized using transmission electron microscopy (TEM), X‐ray diffraction (XRD), and atomic force microscopy (AFM). The crystallinity and surface roughness increases with an increasing clay content in the PVAC nanocomposite membrane. Compared with the pure poly(vinyl alcohol) (PVA) membrane, the hybrid nanocomposite membrane (PVAC) shows an improvement in the thermal stability and the prevention of the water‐soluble property. The oxygen permeability and the water‐vapor permeation rate decreases with an increasing clay content (1–3 wt %) in the PVAC nanocomposite membranes. In addition, the effects of the clay content on the vapor‐permeation performance of an aqueous ethanol solution through the PVAC nanocomposite membranes was also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3632–3638, 2003     

Surface free‐energy analysis of poly(N‐vinyl‐2‐pyrrolidone–crotonic acid) copolymers prepared by γ‐ray‐induced polymerization technique

Composite hydrogels of pectin and polyacrylamide were synthesized and evaluated by scanning electron microscopy, atomic force microscopy, light microscopy, and dynamic mechanical analysis. The crosslinking polymerization of acrylamide in pectin solution resulted in a composite having a macroporous pectin domain with an interstitial polyacrylamide domain. This composite had improved mechanical properties compared to those of either polymer alone, and it absorbed and retained more water than crosslinked polyacrylamide alone. Furthermore, crosslinking polymerization of acrylamide in an existing pectinate scaffold resulted in a double‐network architecture, where filamentous polyacrylamide networks penetrated through pores of the pectin scaffold. It was found that pectins dictated the features of microstructure in the composites through regulating the coordination of phase separation of the two components and water partition between the two phases. Results from this study highlight potential new uses of pectins in protecting the physical structure of environmentally sensitive polymers from mechanical damage related to freezing, lyophilization, and other conditions experienced during their use in biomedical and industrial products. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1893–1901, 2004     

FT‐IR Study of Blends and Complexes of Poly(mono n‐alkyl itaconates) with Poly(N,N‐dimethylacrylamide) and Poly(ethyloxazoline)

Summary: This paper reports an FT‐IR study of blends and complexes of poly(mono n‐alkyl itaconates) with poly(N,N‐dimethylacrylamide) (PDMA) and poly(ethyloxazoline) (PEOX). Strong hydrogen bonding has been found and both polybases have shown similar acceptor strengths. The extent of the interassociation has been estimated by spectral curve fitting of the polybase carbonyl band. The influences of the solvent medium and alkyl side group length of the poly(mono n‐alkyl itaconate) on the interassociation extents have been discussed. Blend and complex interassociation behavior has been compared too. Results show that media influences the interassociation degree in systems with PDMA, but has negligible influence in systems with PEOX. Moreover, the interassociation degree in blends with PEOX does not depend on the length of the poly(monoalkyl itaconate) side group, while an interassociating ability loss is observed in blends with PDMA as the side group size of the polyacid increases. This different behavior is attributed to the greater interspacing between vicinal carbonyl groups in PEOX. Anyway, this band shows conformational sensitivity and reflects the conformational changes that are forced to adopt as the steric hindrances present in the medium (due to the bulky side groups of the polyacids) increase.

Auto scaled carbonyl stretching region for PMBuI/PEOX complexes.     

Poly(N‐hydroxyethyl acrylamide)‐b‐polystyrene by combination of ATRP and aminolysis processes

Block copolymers of very hydrophilic poly(N‐hydroxyethyl acrylamide) (PHEAA) with polystyrene (PS) were successfully synthesized by sequential atom transfer radical polymerization of ethyl acrylate (EA) and styrene monomers and subsequent aminolysis of the acrylic block with ethanolamine. Quantitative aminolysis of poly(ethyl acrylate) (PEA) block yielded poly(N‐hydroxyethyl acrylamide)‐b‐polystyrene in well‐defined structures, as evidenced by Fourier transform infrared spectroscopy (FTIR) and ¹H‐NMR spectroscopy techniques. Three copolymers with constant chain length of PHEAA (degree of polymerization: 80) and PS blocks with 21, 74, and 121 repeating units were prepared by this method. Among those, the block copolymer with 21 styrene repeating units showed excellent micellation behavior in water without phase inversion below 100°C, as inferred from dynamical light scattering, environmental scanning electron microscopy, and fluorescence measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(Caprolactone)‐Poly(N‐Isopropyl Acrylamide)‐Fe3O4 Magnetic Nanofibrous Structure with Stimuli Responsive Drug Release

Poly(caprolactone; PCL)—poly(N‐isopropylacrylamie; PNIPAAm)—Fe₃O₄ fiber, that can be magnetically actuated, is reported. Here, a structure is engineered that can be utilized as a smart carrier for the release of chemotherapeutic drug via magneto‐thermal activation, with the aid of magnetic nanoparticles (MNPs). The magnetic measurement of the fibers revealed saturation magnetization values within the range of 1.2–2.2 emu g^?1. The magnetic PCL‐PNIPAAm‐Fe₃O₄ scaffold shows a specific loss power value of 4.19 W g^?1 at 20 wt% MNPs. A temperature increase of 40 °C led to a 600% swelling after only 3 h. Doxorubicin (DOX) as a model drug, demonstrates a controllable drug release profile. 39% ± 0.92 of the total drug loaded is released after 96 h at 37 °C, while 25% drug release in 3 h at 40 °C is detected. Cytotoxicity results show no significant difference in cell attachment efficiency between the MNP‐loaded fibers and control while the DOX‐loaded fibers effectively inhibited cell proliferation at 24 h matching the drug release profile. The noncytotoxic effect, coupled with the magneto‐thermal property and controlled drug release, renders excellent potential for these fibers to be used as a smart drug‐release agent for localized cancer therapy.     

Physical properties of poly(vinyl chloride)–grafted N‐isopropylacrylamide graft copolymers and corresponding polyblends

The physical properties of poly(vinyl chloride) (PVC) and poly(N‐isopropylacrylamide) [poly(NIPAAm)] blend systems, and their corresponding graft copolymers such as PVC‐g‐NIPAAm, were investigated in this work. The compatible range for PVC–poly(NIPAAm) blend systems is less than 15 wt % poly(NIPAAm). The water absorbencies for the grafted films increase with increase in graft percentage. The water absorbencies for the blend systems increase with increase in poly(NIPAAm) content within the compatible range for the blends, but the absorbencies decrease when the amount of poly(NIPAAm) is more than the compatible range in the blend system. The tensile strengths for the graft copolymers are larger than the corresponding blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 170–178, 2000     

Functionalization of Poly(propylene) Fabric with 4‐Vinylpyridine,N,N‐Dimethylacrylamide and Styrene by γ‐Radiation‐Induced Grafting in an Aqueous Environment

Summary: VP and co‐monomers DMAAm and ST were successfully grafted onto a PP fabric in an emulsion copolymerization process initiated by γ‐radiation. The radiation dose, concentration of VP, the ratio of VP/DMAAm and VP/ST in the reaction solution, and the reaction temperature dependent graft copolymerization were investigated. The order of dependence of the initial rate of grafting on the radiation dose was found to be in the range of 1.2 to 0.93 for VP; 0.84 to 0.70 for VP/DMAAm and for VP/ST was in the range of 0.59 to 0.41. The activation energy of the graft copolymer reaction was determined to be 40.18 J · mol^?1 for 0.464 mol · L^?1 VP. In the case of co‐monomer mixtures (VP/DMAAm: 0.464/0.5) the energy of activation was noticeably higher at 49.71 J · mol^?1 while for VP/ST (0.464/0.436) the activation energy was same as that of VP. XRD results showed that overall crystallinity significantly decreased with the increase of graft weight with a noticeable change in the chemical structure of the PP, indicating that the graft copolymer reaction was taking place both in the amorphous and crystalline regions of PP. A similar characteristic behavior was also obtained by DSC, which revealed the presence of an endotherm process in the range of 25 to 130 °C depending on the degree of grafting, attributed to the grafted chains of the monomer/co‐monomers. In order to determine the graft copolymer reaction of VP, DMAAm and ST onto the backbone of PP, the reaction products were characterized by FTIR spectroscopy. A good correlation was found between changes of crystallinity and level of graft copolymerization as determined by WAXRD and DSC.

Typical XRD traces of as‐received PP fabric (PPF) and grafted with VP (PPF‐g‐VP).