L. Terlemezyan

Bulgarian Academy of Sciences, Ulpia Serdica, Sofia-Capital, Bulgaria

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Publications (69)162.55 Total impact

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    Bernhard Wessling · L. Terlemezyan

    Full-text · Dataset · Aug 2013
  • Ivo Grabchev · Pavlina Mokreva · Valeria Gancheva · Levon Terlemezyan
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    ABSTRACT: Two new green fluorescence poly(propyleneamine) dendrimers from second generation, comprising eight 1,8-naphthalimide signaling units in their periphery have been synthesized and investigated. Тheir photophysical characteristics have been determined in organic solvents of different polarity. Particular attention has been paid to the spectral characteristics of the solid dendrimer films. The photostability of the dendrimers has also been studied.
    No preview · Article · Apr 2013 · Journal of Molecular Structure
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    ABSTRACT: Organic thin films of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) mixed in 1:1 mass ratio were deposited by spin coating from a chlorobenzene solution. The substrates used were glass and Si wafers. The films were produced for fu- ture application in organic solar cells. After the deposition procedure, the P3HT:PCBM films were annealed in argon atmosphere at different tempera- tures or were kept in the solvent vapour for 10 min in order to stabilize the coat- ings. The films were characterized by Fourier Transform Infrared Spectroscopy (FTIR), optical transmission and reflection spectroscopy, Raman spectroscopy and photoluminescence (PL) measurements. The highest absorption coefficient and best crystallization of the films was obtained upon thermal annealing at 140°C and treatment in solvent vapour. Annealing at temperatures above 140°C gradually destroyed the crystalline order, and annealing at 160°C led to the amorphization of the P3HT in the film. For the purpose of charge separa- tion the best post-deposition treatment appeared to be 60 °C, as demonstrated by the PL measurements. In this case, the best interpenetration of the two constituents of the bulk heterojunction was most probably achieved.
    No preview · Article · Jan 2013 · Comptes rendus de l'Académie bulgare des sciences: sciences mathématiques et naturelles
  • Petar Petrov · Levon Terlemezyan

    No preview · Chapter · Apr 2011
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    ABSTRACT: The synthesis of two polyconjugated graft copolymers based on a poly(fluorene-phenylene) backbone and polystyrene side chains is described here. The two different approaches followed, ATRP growth of side chains from a preformed conjugated backbone and “click” connection of well-defined polymeric chains to the backbone, led to different results in terms of solubility and material properties. While the ATRP method seems to be responsible of a partially cross-linked and nonsoluble copolymer, the “click” approach provides a graft copolymer, which is completely soluble, showing atypical spectroscopic properties that are here elucidated.
    Full-text · Article · Jul 2010 · Macromolecular Chemistry and Physics
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    ABSTRACT: A dipyrromethane functionalized monomer; 5-(4-tert-butylphenyl)dipyrromethane (BPDP) was synthesized. The structure of the monomer was characterized by nuclear magnetic resonance (1H NMR and 13C NMR) and Fourier transform infrared (FTIR) spectroscopies. Electrochemical polymerization of BPDP was performed in acetonitrile (AN)/LiClO4. The resulting conducting polymer was characterized by FTIR spectroscopy and electrical conductivity measurements. Spectroelectrochemical behavior and switching ability of P(BPDP) film were investigated by UV–Vis spectroscopy. P(BPDP) revealed color changes between yellow and blue in the reduced and oxidized states, respectively. In order to investigate electrochromic properties and stability of the P(BPDP) in electrochromic device (ECDs) application, dual type polymer ECD based on P(BPDP) and poly(ethylene dioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV–Vis spectroscopy and cyclic voltammetry.
    Full-text · Article · Aug 2008 · European Polymer Journal
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    ABSTRACT: Polyaniline (PANI) nanotubes were prepared by oxidative polymerization of aniline in the presence of two structure-directing agents—salicylic acid (SA) and sodium dodecyl sulfate (SDS). When using only SA, mainly aggregated nanotube dendrites or coral-like structures have been obtained. Addition of a very small amount of the surfactant SDS, much less than the critical micelle concentration, results in substantial reduction of the aggregated nanotube morphology on the account of isolated PANI nanotubes, which is the favorable structure from the point of view of further modification. In order to make the isolated nanotubes water dispersible, their surface was modified by complex formation (non-covalent grafting) with hydrophilic poly(ethylene oxide)-block-poly(acrylic acid) copolymer. These water-dispersible PANI nanotubes might be good candidates for some biochemical and biomedical applications.
    No preview · Article · May 2008 · Colloid and Polymer Science
  • L. Terlemezyan · P. Mokreva · D. Tsocheva · S. Peneva · K. Berovsky · T. Troev
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    ABSTRACT: The positron lifetime spectroscopy (PLS), a non-destructive characterization method, utilizes positronium (Ps; an electron–positron bound state) as a probe and measures its lifetime in polymer free volumes. For the first time the free volumes have been estimated by PLS in polyaniline (PANI) complexes with various inorganic and organic acids. It was found that the o-Ps lifetime increases and the intensity decreases with increasing ionic radius of the counter-ions in PANI complexes. Obviously, larger counter anions result in enhanced mean size of the voids corresponding to the free volume in the bulk polymer.Electrical conductivity has been measured by conventional four-probe technique. The glass transition temperature and temperature of removal of the absorbed water have been determined by using differential scanning calorimetry. It was established fairly well correlation of the mentioned polymer parameters with the o-Ps lifetime and the free volume of PANI complexes, respectively. The greater free-volume results in a decrease of conductivity, glass transition temperature and temperature of removal of the absorbed water.
    No preview · Article · May 2008 · Radiation Physics and Chemistry
  • T. Tsanov · P. Mokreva · D. Tsocheva · L. Terlemezyan
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    ABSTRACT: The electrical conductivity behavior of polyaniline–poly(ethylene‐co‐vinyl acetate) (PANI–EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (Φc) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5 wt.%) increased by several (ca. 5) orders of magnitude. It was found that the PANI phase undergoes a flocculation process subsequently resulting in the formation of conductive pathways and a continuous network. Besides, the shape of percolation curves was found to change during storage of the films. Decreased conductivity deviations were registered for blends of low PANI content (
    No preview · Article · Aug 2007 · Journal of Macromolecular Science Part C Polymer Reviews
  • Dimitrinka Tsocheva · Pavlina Mokreva · Levon Terlemezyan
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    ABSTRACT: A study on the thermal stability, thermodynamical parameters, especially relaxation transition temperature (Tg), and their change upon irreversible reactions (crosslinking, postpolymerization, decomposition, etc.) taking place on heating of the undoped homo- and copolymers of aniline and o-methoxyaniline was performed by using differential scanning calorimetry. It was found that polyaniline and its oligomers might be responsible for the postpolymerization process observed on heating thermograms of the polymers in their emeraldine base form. It can be stated that the proceeding of this process appears to be a reason for the higher thermal stability of polyaniline when compared with poly(o-methoxyaniline). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2729–2734, 2007
    No preview · Article · May 2007 · Journal of Applied Polymer Science
  • Stoyanka Stoeva · Dimitrinka Tsocheva · L. Terlemezyan
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    ABSTRACT: The melting behavior of solid-state chlorinated polyethylene samples of various average molar mass has been studied by employing the differential scanning calorimetry method. Both the thermal and thermodynamic characteristics of the as-prepared chlorinated powdery polymer samples were found to be essentially different, compared to those of the melt-crystallized ones. The changes in the corresponding values depended mainly on the content of the comonomer units such as chloromethylene and dichloromethylene groups and their distribution along the polymer chains. Therefore, it can be assumed that the order of the polymer crystals arrangement is disturbed in the course of both the chlorination process and the subsequent melt crystallization.
    No preview · Article · Aug 2006 · Journal of Thermal Analysis and Calorimetry
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    ABSTRACT: High-conversion (HC) copolymers of aniline and o-methoxyaniline (o-anizidine) were synthesized for the first time by chemical oxidative copolymerization using various polymerization techniques (simultaneous or consecutive introduction of comonomers into the polymerizing system). Low-conversion (LC) copolymers have also been synthesized for comparison. The polymers obtained were characterized using 1H-NMR, infrared, and electronic absorption spectroscopy, differential scanning calorimetry, and electrical conductivity measurements. Solubility characteristics and composition of different fractions of the copolymers were also determined. It was shown that in contrast to the LC copolymers, HC copolymers reveal relatively poor solubility. Electrical conductivity of copolymers and also of o-methoxyaniline homopolymer is lower compared to polyaniline, which correlates with notable hypsochromic (blue) shift of the bands in electronic absorption spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 75–81, 2006
    Full-text · Article · Jan 2006 · Journal of Applied Polymer Science
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    ABSTRACT: High-conversion (HC) copolymers of aniline and o-methoxyaniline (o-anizidine) were synthesized for the first time by chemical oxidative copolymerization by using various polymerization techniques (simultaneous or consecutive introduction of comonomers into the polymerizing system). Low-conversion (LC) copolymers have also been synthesized for comparison. The polymers obtained were characterized by using 1H-NMR, infrared, and electronic absorption spectroscopy; differential scanning calorimetry; and electrical conductivity measurements. Solubility characteristics and composition of different fractions of the copolymers were also determined. It was shown that, in contrast to the LC copolymers, HC copolymers reveal relatively poor solubility. Electrical conductivity of copolymers and also of o-methoxyaniline homopolymer is lower as compared to polyaniline, which correlates with notable hypsochromic (blue) shift of the bands in electronic absorption spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1822–1828, 2005
    No preview · Article · Nov 2005 · Journal of Applied Polymer Science
  • D. Tsocheva · L. Terlemezyan
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    ABSTRACT: Summary Electrically conductive composites containing high density polyethylene (HDPE) and polyaniline (PANI) - dodecylbenzenesulfonic acid (DBSA) complex were prepared in situ by bulk oxidative polymerization of aniline (ANI) in presence of DBSA. Their thermal behaviour and crystallinity parameters were studied for the first time by using differential scanning calorimetry (DSC). It was found that the presence of the conductive complex does not affect the crystalline structure of the matrix polymer neither during in situ polymerization of ANI in powdered HDPE nor upon heating of HDPE/PANI·DBSA composite up to 180°C followed by fast cooling.
    No preview · Article · Jul 2005 · Journal of Thermal Analysis and Calorimetry
  • D. Tsocheva · L. Terlemezyan
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    ABSTRACT: Crystallinity parameters and changes in the crystalline morphology with temperature of an electrically conductive composite containing ultrahigh molecular mass polyethylene (UHMMPE) and polyaniline (PANI) doped with dodecylbenzenesulfonic acid (DBSA) are studied for the first time by using differential scanning calorimetry and wide-angle X-ray diffraction. It is found that during the melting of UHMMPE crystals PANI partially penetrates in the amorphous phase of the matrix polymer. Since the composite is found to be thermally stable up to ca. 270°C, it can be suggested that it would be processable without loosing conductivity at temperatures much higher than the melting temperature of UHMMPE.
    No preview · Article · Jan 2004 · Journal of Thermal Analysis and Calorimetry
  • L. Terlemezyan · M. Radenkov · P. Mokreva · P. Radenkov · A. Atanasov
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    ABSTRACT: Electrically conductive polymer composites were prepared in situ (one-stage procedure) for the first time by oxidative bulk polymerization of aniline in the presence of powdered ultra-high-molecular-weight polyethylene (UHMWPE). For the sake of comparison, UHMWPE/polyaniline (PANI) composites were also prepared by two-stage procedures: (a) by mixing powdered UHMWPE with preliminary prepared aqueous dispersion of the complex of PANI with dodecylbenzene sulfonic acid (DBSA); and (b) by mixing 2.5% xylene "solution " of the PANI. DBSA complex obtained by drying aqueous dispersion synthesized as mentioned above. High electrical conductivity (10-3 - 10-4 S/cm) was attained at a quite low PANI content (1.5 mass%) for composites obtained both by the one-stage procedure, as well as by two-stage procedures using previously prepared PANI.DBSA complex. Further increase in PANI content does not result in enhanced conductivity due to extremely high UHMWPE melt viscosity hampering the possibility for improvement of the conductive network which is the case in melt processing of PANI composites with other polyolefins. Tensile properties of hot pressed UHMWPE deteriorate on adding the PANI complex approximately in the same extent or less as compared to literature data for gel processed fibers and solution cast films of analogous composites.
    No preview · Article · Jun 2003 · Journal of Polymer Materials
  • B. Ganchev · D. Straková · P. Kratochvíl · L. Terlemezyan · M. Mikhailov
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    ABSTRACT: Statistical copolymers of styrene and acrylonitrile, covering a wide range of compositions, were synthetized by emulsion polymerization conducted to both low and high conversion. The weight-average molecular weights of the copolymers were determined by light scattering and correlated with intrinsic viscosities measured in methyl ethyl ketone and/or dimethyl formamide solutions. The copolymers polymerized in emulsion are suggested to consist of macromolecules with long chain branching.Statistische Styren-Acrylnitril-Copolymere wurden durch Emulsionspolymerisation in einem breiten Bereich der Zusammensetzung sowohl bei niedrigen als auch bei hohen Umsätzen hergestellt. Die Massenmittel der relativen Molekülmassen der Copolymere wurden mittels Lichtstreuung ermittelt und mit den in Methylethylketon- bzw. Dimethylformamid-Lösungen gemessenen Grenzviskositätszahlen in Beziehung gebracht. Es wird gefolgert, daß die in Emulsion polymerisierten Copolymere aus Makromolekülen mit Langkettenverzweigungen bestehen.
    No preview · Article · Apr 2003 · Acta Polymerica
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    S. Ivanov · P. Mokreva · V. Tsakova · L. Terlemezyan
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    ABSTRACT: Polyaniline (PAni) coatings are synthesized polymerizing aniline chemically, by oxidation in presence of (NH4)2S2O8, and electrochemically, by using a pulse potentiostatic procedure. Both types of PAni coatings are compared with respect to their potentiodynamic behavior, electrochemical stability and surface morphology. Additional comparison is made by investigating the electrocrystallisation of copper. The chemically and electrochemically PAni coatings exhibit different surface morphologies but nevertheless show identical redox behavior and stability with respect to multiple cycling. The different PAni morphologies have a marked influence on the metal crystallization process, the chemical coatings allowing for an easier copper nucleation and growth.
    Full-text · Article · Jan 2003 · Thin Solid Films
  • D. Tsocheva · T. Tsanov · L. Terlemezyan
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    ABSTRACT: The long-term environmental ageing of conductive composite films containing ethylene-co-vinyl-acetate (EVA) copolymer and a complex of polyaniline (PANI) and dodecylbenzenesulfonic acid (DBSA) was studied by using differential scanning calorimetry (DSC). We assume that both phase separation and crosslinking of PANI main chains occur in the systems. On the other hand, the competition between PANI–DBSA complex self-organization and crystallization of EVA matrix result in structural changes and formation of continuous conductive network, responsible for significantly increased (ca five orders of magnitude) electrical conductivity of the aged films.
    No preview · Article · Apr 2002 · Journal of Thermal Analysis and Calorimetry
  • L. Terlemezyan · P. Mokreva
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    ABSTRACT: Electroactive polymer blends of high density polyethylene and polyaniline as the conductive constituent are prepared for the first time in situ by oxidative bulk-poly-merization of aniline in the presence of polyethylene and dodecylbenzenesulfonic acid. The blends reveal substantially higher electrical conductivity as compared to the data found in literature for analogous blends obtained previously by casting solutions or by melt extrusion of polyethylene and preliminary prepared polyaniline. The conductive constituent does not deteriorate the melt-processing performance of the matrix polymer and the blends are processable without losing conductivity.
    No preview · Article · Jan 2002 · International Journal of Polymeric Materials