Progress in conducting/semiconducting and redox-active oligomers and polymers of arylamines

Recent advances in synthesis, characterization and application of the selected conducting/semiconducting and redox-active oligomers and polymers of arylamines are reviewed. A brief historical background of the selected topics is given. The overview of the preparation, structure and properties of polyaniline, substituted polyanilines, especially those obtained by the oxidative polymerization of p-substituted anilines, poly(1-aminonaphthalene) and its derivatives, carbocyclic and heterocyclic polyaryldiamines such as poly(p-phenylenediamine) and polydiaminoacridines, is presented. The mechanism of formation of polyaniline nanostructures is discussed. Recent approaches to the preparation of one-dimensional polyaniline nanostructures are concisely reviewed, with special attention paid to the template-free falling-pH method. Current and potential future applications of oligo/polyarylamines are briefly discussed. [Projekat Ministarstva nauke Republike Srbije, br. OI 172043

Polyaniline nanostructures synthesizedby the dopant-free oxidative polymerization of aniline

Istraživanja u ovoj doktorskoj disertaciji obuhvataju: sinteze nanostruktura polianilina (PANI) oksidativnom hemijskom polimerizacijom anilina (ANI) sa amonijum peroksidisulfatom (APS) u razliĉitim sistemima bez dodatka kiseline i templata, u uslovima opadajućeg pH, karakterizaciju sintetisanih PANI razliĉitim fiziĉkohemijskim metodama i prouĉavanje mehanizma sinteze i formiranja PANI nanostruktura u ispitivanim sistemima. Sinteze PANI su uraĊene korišćenjem jednostavnih, ekonomiĉnih i ekološki prihvatljivih procedura i supstancija. Akcenat je bio na korišćenju što manjeg broja hemikalija za odgovarajuće sintetiĉke procedure. Pored oksidacionog sredstva (APS) i monomera (ANI), u reakcione sisteme su ukljuĉeni razliĉiti organski rastvaraĉi, hidrolizovani kolagen (biološki materijal), ili FeSO4 (katalizator). Idealan molski odnos APS i ANI od 1,25 za sintezu elektroprovodnog oblika PANI, emeraldin soli, je upotrebljen u svim sintezama. Varirani su sledeći uslovi: poĉetna pH vrednost, dužina trajanja sinteze, uslovi mešanja reakcione smeše i organski rastvaraĉi. Rezultati dobijeni u okviru ove doktroske teze se mogu podeliti u sledećih pet celina: 1) Oksidacija ANI vršena je pomoću APS u sistemima bez dodatka kiseline i templata u kojima su koncentracije oba reaktanta bile niske (CANI = 0,02 i 0,05 M). Reakcija je praćena merenjem temperature i pH. Karakteristike polimerizacije i sintetisanih PANI uporeĊivane su sa analognim sintezama u koncentrovanim sistemima (CANI = 0,1 i 0,2 M). Skenirajućom elektronskom mikroskopijom (SEM) je utvrĊeno da se nanostrukturni PANI sulfat/hidrogen sulfat, sintetisan pri niskim koncentracijama reaktanata, sastoji od mreže nanoštapića i nanogranula. Molekulska struktura sintetisanih i dedopiranih PANI uzoraka, ispitivana elementarnom analizom, infracrvenom spektroskopijom sa furijeovom transformacijom (FTIR), ramanskom, ultraljubiĉastom-vidljivom (UV-Vis) i elektronskom paramagnetnom rezonantnom (EPR) spektroskopijom, je znaĉajno drugaĉija u poreĊenju sa molekulskom strukturom nanostrukturnih PANI sulfata/hidrogen sulfata sintetisanih u koncentrovanim...The research in this Ph.D. thesis includes: synthesis of nanostructured polyaniline (PANI) by the chemical oxidative polymerization of aniline (ANI) with ammonium peroxydisulfate (APS) in different systems with the use of dopant-free template-free falling-pH method, characterization of the synthesized PANI by various physicochemical methods and the study of the mechanism of synthesis and the formation of PANI nanostructures in investigated systems. Syntheses of PANI were performed using simple, cost-effective and environmentally friendly procedures and substances. The emphasis was on using not as many chemicals for the proper synthetic procedure. Besides the oxidant (APS) and monomer (ANI), in the reaction mixtures were included various organic solvents, hydrolyzed collagen (a biological system) or FeSO4 (catalysator). The optimal molar ratio of the ANI and APS of 1.25 for the electroconductive emeraldin salt form of PANI syntheses was used in all synthetic procedures. The initial pH value, the length of the synthesis, stirring conditions of the reaction mixture and the organic solvents were varied. The results obtained within this thesis can be divided into the following five sections: 1) The oxidation of ANI with APS was conducted in diluted aqueous systems (CANI = 0,02 i 0,05 M) without added acid and template (dilute dopant-free template-free method). The reaction was monitored by measuring the temperature and pH. The characteristics of the polymerization and the synthesized PANI were compared to analog synthesis in concentrated systems (CANI = 0,1 i 0,2 M). Scanning electron microscopy (SEM) revealed that nanostructured PANI sulfate/hydrogen sulfate, synthesized in low concentration conditions, consists of a network of nanorods and nanogranules.The molecular structure of PANI sulfate/hydrogen sulfate prepared in diluted ANI solutions considerably different in comparison to the structure of PANI sulfate/hydrogen sulfate prepared in concentrated aqueous ANI was discovered by elemental analysis, Fourier transform infrared spectroscopic (FTIR), Raman, ultra-violet (UV–Vis) and electron paramagnetic resonance (EPR) spectroscopic studies. The..

Položaj prve dame u američkom pravu

U skladu sa predsedničkim sistemom vlasti koji postoji u SAD i dugogodišnjom tradicijom, uloga prve dame najviše je naglašena u ovoj zemlji, iako njen položaj, kao i u drugim zemljama, nije uređen Ustavom, niti je institucionalizovan. Značaj prve dame potvrđen je u praksi, budući da ona ima svoju kancelariju u okviru Bele kuće, sekretarijat, osoblje, pravo na obezbeđenje i dr., a brojne pogodnosti predviđene su i za supruge bivših predsednika. U skladu sa tradicijom jeste i njena osnovna dužnost da bude domaćica Bele kuće, kao i uloga u organizovanju humanitarnih, odnosno dobrotvornih akcija, čime se potvrđuje njen protokolaran, odnosno ceremonijalan položaj. U radu se zato daje prikaz odredaba američkog prava kojima se uređuju prava i obaveze supruge predsednika, uz primere iz prakse koji se odnose na njen položaj

Design of an amino-functionalized chelating macroporous copolymer poly(GMA-co-EGDMA) for the sorption of Cu(II) ions

Polymer-based, highly porous nanocomposites with functionalized ligands attached to the core structure are extremely efficient in the detection, removal and recovery of metals through the process of sorption. Quantum-chemical models could be helpful for sorption process analyses. The sorption of Cu(II) ions by amino-functionalized chelating macroporous copolymers poly(GMA-co-EGDMA)-amine and sorption selectivity of the subject copolymers, ethylenediamine (en), diethylenetriamine (dien) and triethylenetetramine (trien), were successfully modelled by quantum chemical calculations. Considering the crystal structures from CSD and experimental conditions during the formation of metal complexes, the most frequent mononuclear complexes are those with the tetradentate teta ligand, while binuclear complexes are formed when the metal ion is in large excess. Although the en-copolymer was the most effective functionalized one, higher maximum sorption capacities (Qmax) were observed for the dien- and trien-copolymers, due to their abilities to form binuclear complexes. The enthalpy term has the greatest contribution to the total Gibbs energy change of reaction for the formation of mononuclear Cu(II) complexes (ΔGaq), while the solvation energy of the reaction has the greatest contribution in the formation of binuclear complexes. The results of the study indicate that small amines with the ability to form binuclear complex are the best choice for functionalization of the considered copolymer

Comparative study of W(VI) and Cr(VI) oxyanions binding ability with magnetic polymer nanocomposite

Magnetite particles are widely used as sorbents for removal of heavy metal ions, organic dyes, drug delivery, cell labelling, magnetic resonance imaging, sensing, etc. [1,2]. Also, the functionalization of polymer by specific ligands enables customizing these composites for specific applications. Magnetic crosslinked macroporous copolymer of glycidyl methacrylate, GMA, and ethylene glycol dimethacrylate, EGDMA, mPGME was synthesized by suspension copolymerisation of GMA and EGDMA, in the presence of inert component (mixture of cyclohexanol and aliphatic alcohol) [3] and magnetite nanoparticles coated with (3-aminopropyl)trimethoxysilane (APTMS) as silanization agent. The sample was additionally functionalized with diethylene triamine mPGME-deta. Magnetic amino-functionalized copolymer was fully characterized in terms of its structural and magnetic properties using: FTIR analysis, SEM/EDX, XRD and SQUID magnetometry. Synthesized magnetic macroporous copolymer mPGME-deta was tested as sorbent of W(VI) and Cr(VI) oxyanions from diluted aqueous solutions (Ci=25 ppm) in a batch system, under uncompetitive conditions, at room temperature (T=25 °C). The oxyanions concentrations in solution after 60 min of sorption, were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The maximal experimental values of oxyanions sorption capacities (Qmax μmol/g) were compared with theoretically values determined by theoretical modeling, using quantum-chemical methods: Density Functional Theory (DFT), statistic analysis of the crystal structure extracted from the Cambridge Structural Database (CSD) and by implicit solvation model (SMD). It was found that the process is spontaneous and exothermic, and that the active sites of magnetic copolymer sorbent are amino groups (of diethylenetriamine and APTMS) which forms electrostatic interactions with oxianions W(VI) and Cr(VI)

Impact of dental implant insertion method on the peri-implant bone tissue: Experimental study

Background/Aim. The function of dental implants depends on their stability in bone tissue over extended period of time, i.e. on osseointegration. The process through which osseointegration is achieved depends on several factors, surgical insertion method being one of them. The aim of this study was to histopathologically compare the impact of the surgical method of implant insertion on the peri-implant bone tissue. Methods. The experiment was performed on 9 dogs. Eight weeks following the extraction of lower premolars implants were inserted using the one-stage method on the right mandibular side and two-stage method on the left side. Three months after implantation the animals were sacrificed. Three distinct regions of bone tissue were histopathologically analyzed, the results were scored and compared. Results. In the specimens of one-stage implants increased amount of collagen fibers was found in 5 specimens where tissue necrosis was also observed. Only moderate osteoblastic activity was found in 3 sections. The analysis of bone-to-implant contact region revealed statistically significantly better results regarding the amount of collagen tissue fibers for the implants inserted in the two-stage method (Wa = 59 < 66,5, α = 0.05), but necrosis was found in all specimens, and no osteoblastic activity. Histopathological analysis of bone-implant interface of one-stage implants revealed increased amount of collagen fibers in all specimens, moderate osteoblastic activity and neovascularization in 2 specimens. No inflammation was observed. The analysis of two-stage implants revealed a marked increase of collagen fibers in 5 specimens, inflammation and bone necrosis were found in only one specimen. There were no statistically significant differences between the two methods regarding bone-implant interface region. Histopathological analysis of bone tissue adjacent to the one-stage implant revealed moderate increase of collagen tissue in only 1 specimen, moderate increase of osteoblasts and osteocytes in 3 specimens. No necrotic tissue was found. The analyzed specimens of bone adjacent to two-stage implants revealed a moderate increase in the number of osteocytes in 3 and a marked increase in 6 specimens respectively. This difference was statistically significant (Wb = 106.5 > 105, α = 0.05). No necrosis and osteoblastic activity were observed. Conclusion. Better results were achieved by the two-stage method in bone-to-implant contact region regarding the amount of collagen tissue, while the results were identical regarding the osteoblastic activity and bone tissue necrosis. There was no difference between the methods in the bone-implant interface region. In the bone tissue adjacent to the implant the results were identical regarding the amount of collagen tissue, osteoblastic reaction and bone tissue necrosis, while better results were achieved by the two-stage method regarding the number of osteocytes

Korelacija eksperimentalnih podataka sa teorijskim predviđanjem sorpcije jona teških metala na makroporoznom amino-funkcionalizovanom sorbentu

Over the decades, various sorbents have been used in the treatment of wastewater contaminated with heavy metal ions, which seriously endanger the living world. Macroporous functional polymers show a high affinity for sorption of these ions, where sorption efficiency and selectivity directly depend on the nature of the functional groups of sorbent and metal ions. In this study, we performed a correlation of theoretical predictions and experimental data obtained by investigation of Cu2+, Co2+, Ni2+ and Cd2+ cations sorption under competitive and uncompetitive conditions from aqueous solutions on macroporous amino-functionalized sorbent poly(glycidyl methacrylate-coethylene glycol dimethacrylate), PGME-deta. Quantum-chemical calculations estimated the binding energies of metal ions to the active sites of the sorbent, on the model systems of individual fragments, composed of metal ions and ligands, based on statistical analysis of data obtained from crystal structures. By this theoretical approach, the high degree of correlation with experimental data was observed for mono-component system.Decenijama se različiti sorbenti primenjuju za tretman otpadnih voda kontaminiranih jonima teških metala, koji ozbiljno ugrožavaju živi svet. Makroporozni funkcionalni polimeri pokazuju visok afinitet za jone teških metala, pri čemu efikasnost sorpcije i selektivnost direktno zavise od prirode funkcionalnih grupa sorbenta i jona metala. U radu je predstavljena korelacija teorijskih predviđanja i eksperimentalnih podataka dobijenih ispitivanjem sorpcije katjona Cu2+, Co2+, Ni2+ i Cd2+ u konkurentnim i nekonkurentnim uslovima u vodenom rastvoru na makroporoznom amino-funkcionalizovanom sorbentu poli(glicidil-metakrilat-co-etilen glikol dimetakrilat), PGME-deta. Kvantno-hemijskim proračunima procenjene su energije vezivanja metalnih jona za aktivna mesta sorbenta na model sistemima pojedinačnih fragmenata, metal-ligand, dobijenih statističkom analizom podataka baze kristalnih struktura. Ovakav teorijski pristup pokazao je visok stepen korelacije sa eksperimentalnim podacima u jednokomponentnim sistemima

Fluorination of aliphatic compounds. Driving force in crystal structures

Statistical analysis of crystal structures from CSD (Crystallographic database) has shown the F...F contacts are the second group of interactions (23050 structures), immediately after the hydrogen bonds (43397 structures), that are mainly of aliphatic C−H...F type. There is no clear tendency of F...F contacts toward some certain values of d parameter, but it is possible to notice noticeable clear tendency of numerous structures to d values greater than 2.9 Å. There is a pronounced maximum in the range of torsion angle T from 160 to 180° corresponding to trans orientation of interacting C−F and X−Y fragments.На основу анализе кристалних структура преузетих из Кембричке базе кристалографских података (CSD) показано је да се алифтичне C−H...F водоничне везе издвајају као најбројније интеракције флуорованих алифатичних група (43397 стуктура). Далеко испод (23050 структура), на другом месту су F...F интеракције. Уочљиво је да су вредности F...F растојања (d параметар) претежно изнад 2,9 Å. Међутим, не постоји јасно изражена тенденција према одређеној вредности d параметра. Пошто се за највећи број структура вредности торзионог угла C-F-X-Y (Т параметар) крећу између 160 и 180° може се закључити да интерагујуће C−F и X−Y групе међусобно заузимају trans оријентациј

6-hydroxydopamine lesions of the striatum lead to the alterations of dopamine receptor mrna in parkinsonian rats

The effects of four-site intrastriatal 6-hydroxydopamine (6-OHDA) lesions were examined in adult male rats. Five days after the lesions the animals were checked for specific rotational behavior induced by middle dose of amphetamine and the results confirmed the effectiveness of the lesions. The RNAs from the striatum were isolated at different time points after the lesion, and the RT-PCR analyse were performed for the D1 and D2 receptor mRNA. The results show a decline in the D2 receptor mRNA level (40%) at 6 h and 24 h points while this change was not observed seven days after the lesion. In contrast, no statistically significant changes in the level of the D1 receptor mRNA after the lesion at any time point were found.Ispitivani su efekti četiri ubodne 6-hidroksidopaminske (6-OHDA) lezije striatuma kod odraslih mužjaka pacova. Pet dana nakon lezije, životinje su testirane na specifično rotaciono ponaš anje pod uticajem srednje doze amfetamina i rezultati su potvrdili efikasnost lezije. RNK iz striatuma su izolovane u različitim vremenskim tačkama nakon lezije i urađena je RT-PCR analiza iRNK za D1 i D2 dopaminske receptore. Rezultati pokazuju smanjivanje nivoa iRNK za D2 receptor (40%) 6 h i 24 h nakon lezije, dok sedam dana nakon lezije nema promena. Za razliku od ovih rezultata, u nivou iRNK za D1 receptor ne postoje statistički značajne razlike u bilo kojoj vremenskoj tački

Electrochemical Crosslinking of Alginate—Towards Doped Carbons for Oxygen Reduction

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na2S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na2S treated/untreated samples. The most positive onset potential (−0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e− reduction pathway at low overpotentials and shifted towards complete 4e− reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering