Characteristics of rectifying devices with thin films of polyphthalocyanine

Chemically and thermally stable thin films of polyphthalocyanine were prepared by a simple evaporation-polymerization method. The rectifying characteristics of metal/semiconductor/metal (MSM) type sandwich devices with the film were studied. A Schottky type device metal (Cu, Al, Ti)/polyphthalocyanine/Cu shows reproducible rectifying characteristics when Ti is selected as a counter electrode. The reproducibility is improved by pre-oxidation treatment of the surface of Cu substrate. Best electric parameters for the device are as follows: rectifying ratio = 14; threshold potential difference = 0,61 V; saturation current = 2,5 · 10^?6 A · cm^?2; barrier height = 0,75 eV; diode ideality parameter = 4,23. Doping of five kinds of quinones [p-benzoquinone (p-BQ), tetrabromo-p-benzoquinone (p-TBBQ) tetrachloro-p-benzoquinone (p-TCBQ) tetrachloro-o-benzoquinone (o-TCBQ) 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)] and 2,5-cyclohexadien-1,4-diylidenedimalodinitrile (TNCR) in thin films of polyphthalocyanine affected electrocharacteristics in some cases. The diode ideality parameter decreases to 2,17 at 0,90 · 10^?6 mol · cm^?1 of p-TBBQ, and the rectifying ratio increases to about fourteen times by doping p-TBBQ and p-TCBQ. The doped device shows a rectifying response up to 1 kHz.     

The interaction between polymerization initiators and inhibitors in solution, 6. The mechanism of interaction of aroyl peroxides with hydroquinone in chloroform and acetonitrile

The mechanism of the reaction of aroyl peroxides 2a–f with hydroquinone in a polar (acetonitrile) and a nonpolar (chloroform) solvent was investigated by isolation and identification of the reaction products. In acetonitrile, the products were composed of p-benzoquinone, the corresponding aromatic acids, their decarboxylation products, and quinonoid resins containing benzoyloxy groups. In chloroform, the same products were also isolated together with crystalline quinonoid derivatives. The latter were identified to be the 2,5-dibenzoyloxy derivatives of p-benzoquinone. Only in case of 2,4-dichlorobenzoyl peroxide ( 2f ) the quinonoid product was found to be the phenyl and not the ester derivative of p-benzoquinone. The ester derivatives are formed by interaction of the aroyloxy cation 5 with the hydrochinone anion ( 1 ) and not through an intramolecular rearrangement of an unstable perester C , previously assumed for such reactions.     

Synthesis of biodegradable polyesteramides with pendant functional groups

Morpholine-2,5-dione derivatives having substituents with benzyl-protected carboxylic acid, benzyloxycarbonyl-protected amine and p-methoxy-protected thiol groups, respectively, were prepared in 29–58% yield by cyclization of the corresponding N-[(2RS)-bromopropionyl]-L -amino acids. Polyesteramides with protected pendant functional groups were obtained by ring-opening copolymerization of either ?-caprolactone or DL -lactide with morpholine-2,5-dione derivatives having protected functional substituents. The copolymerizations were carried out in the bulk at 130°C using stannous octoate as an initiator and using low mole fractions (0,05, 0,10 and 0,20) of morpholine-2,5-dione derivatives in the feed. The molecular weight of the resulting copolymers ranged from 1,4 to 8,3 · 10⁴. The ring-opening homopolymerization of morpho-line-2,5-dione derivatives with protected functional substituents was not successful. Polyesteramides with either pendant carboxylic acid groups or pendant amine groups were prepared by catalytic hydrogenation of the corresponding protected copolymers. Treatment of copolymers having pendant p-methoxybenzyl-protected thiol groups with trifluoromethanesulfonic acid resulted not only in the removal of the p-methoxybenzyl group but also in severe degradation of the copolymers, due to acidolysis of main-chain ester bonds.     

Cometabolic degradation of o-cresol and 2,6-dimethylphenol by Penicillium frequentans Bi 7/2

o-Cresol induced glucose-grown resting mycelia of Penicillium frequentans Bi 7/2 (ATCC-number: 96048) immediately oxidized o-cresol and other phenols. After precultivation on glucose and phenol degradation started after a lag-phase of 24 hours. Metabolites of o-cresol metabolism were methylhydro-quinone, methyl-p-benzoquinone, 2-methyl-5-hydroxyhydroquinone and 2-methyl-5-hydroxy-p-benzo-quinone. The initial reaction is probably catalyzed by a NADPH dependent hydroxylase which is specific for o-cresol. The metabolism of 2,6-dimethylphenol (2,6-xylenol) occurred via 2,6-dimethylhydroqui-none, 2,6-dimethyl p-benzoquinone, 2,6-dimethyl-3-hydroxyhydroquinone, 2,6-dimethyl-3-hydroxy-p-benzoquinone and 3-methyl-2-hydroxybenzoic acid.     

The interaction between polymerization initiators and inhibitors in solutions. 1. The reaction of benzoyl peroxide with p-benzoquinone in dilute solutions in chlorobenzene

The reaction of benzoyl peroxide with p-benzoquinone in dilute solutions in chlorobenzene was investigated by isolation and identification of some of the reaction products. The reaction is complex; the identified products were phenyl benzoquinone, benzoyloxy benzoquinone, quinhydrone of p-benzoquinone, benzoic acid, and chlorobiphenyls. There was a considerable amount of tarry quinoid products of unspecific physical properties. Neither simple disubstituted quinoid products, nor mono- or di-ethers of hydroquinone were detected. A mechanism based on these findings has been suggested for the reaction.     

Studies of the autoxidation of phenols catalyzed by the cobalt(II) complex of disodium N,N′-bis(salicylidene)-ethylenediamine-5,5′ -disulfonate bound to colloidal anion exchange resin

To overcome mass transfer limitations which are usually encountered on immobilizing active catalysts, cationic latex particles were used as support for the cobalt(II) complex of disodium N,N′-bis(salicylidene)ethylenediamine-5,5′-disulfonate ( 1 ). The cationic latex 2 was prepared by emulsion copolymerization of chloromethylstyrene (m/p-isomer mixture 60/40) and divinylbenzene (m/p-isomer mixture) followed by treatment with trimethylamine. The latexbound catalyst from 1 and 2 was found to considerably increase the reaction rate of the autoxidation of 2,6-di-tert-butylphenol in water as compared with the conventional polymer-free system. Reaction products were identified as the oxidative coupling product 3,3′,5,5′-tetra-tert-butyldiphenoquinone (3,3′,5,5′-tetra-tert-butyl-4,4′-dioxo-1,1′-bicyclohexa-2,5-dienylidene) and 2,6-di-tert-butyl-1,4-benzoquinone. All reactions showed an induction period before the start of dioxygen consumption. The rate of autoxidation in the three-phase mixtures of water, latex particles, and phenol droplets was not affected significantly by the method of mixing. The reaction rate increased as the concentration of 1 increased. Increasing the partial pressure of dioxygen in the range between 0,25 and 1,0 atm (2,53. 10⁴ – 1,01. 10⁵ Pa) gave a small increase in rate. The colloidal latex catalyst from 1 and 2 showed some loss of activity after successive runs.     

Oxidation of 2,6-di-tert-butylphenol by molecular oxygen catalyzed by tetrasodium phthalocyaninatocobalt(II)tetrasulfonate bound to a polymer colloid

Crosslinked cationic latexes based on polystyrene, poly[styrene-co-(methyl methacrylate)] and poly(methyl methacrylate) were prepared by an emulsion polymerization process using 2 mol-% of a quaternary ammonium surfactant monomer. Phthalocyaninatocobalt(II)tetrasulfonate (CoPcTs) bound to these latexes were found to enhance the rate of autoxidation of 2,6-di-tert-butylphenol in water. All CoPcTs-latex catalysts were more active than the water soluble CoPcTsNa₄. The styrene latex bound with CoPcTs was the most active catalyst. The reaction products were identified as the oxidative coupling products 3,3′,5,55′-tetra-tert-butyl-4,4′-dioxo-1,1′-bicyclohexadienylidene (DPQ) and 2,6-di-tert-butyl-1,4-benzoquinone (BQ). The ratio DPQ/BQ was found to be affected by the nature of microenvironment. The rate of autoxidation catalyzed by CoPcTs bound to the styrene latex was found to be zero order with respect to the phenol concentration. The reaction rates increase with pH in the range 7–9. The rate of autoxidation increases with increasing concentration of CoPcTs from 1,0 · 10^?6 to 2,5 · 10^?5 mol/L and then it levels off. At constant concentration of CoPcTs in the reaction mixture, the rate as a function of the weight of latex shows a maximum. The rate shows a linear dependence on partial pressure of dioxygen. Recycling of the latex catalyst results in a reduced activity after successive runs.     

The structure of poly(N-vinylcarbazole) obtained with cationic initiators and electron acceptors as catalysts

Poly(N-vinylcarbazole)s, [poly(l-(N-carbazolyl)ethylene)s], (PVCz's) were prepared under various polymerization conditions. The stereoregularities were estimated by means of ¹³C NMR spectroscopy. Although the stereoregularity of the polymers obtained by BF₃O(C₂H₅)₂ was hardly changed by the polymerization temperature, it changed with the solvent polarity from an isotactic-rich configuration in toluene and CH₂Cl₂ to a syndiotactic-rich configuration in nitrobenzene. The ¹³C NMR spectra of the polymers obtained by organic electron acceptors, support the conclusion that the polymerization by tetracyanoethylene, p-bromanil, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and tetrachlorophthalic anhydride proceed by a cationic mechanism. In the polymerization of N-vinylcarbazole (VCz) with maleic anhydride as an electron acceptor, a small amount of copolymer was obtained together with the homopolymer of VCz. Although the structure of the homopolymers is the same as that of the radically obtained polymer, it is considered that the polymer is formed by a cationic mechanism. The polymerizations of VCz by inorganic compounds, such as ferric nitrate, cupric nitrate, cupric bromide, etc., as catalysts are cationic.     

The interactions between polymerization initiators and inhibitors in solution V. The reaction between benzoyl peroxide and p-benzoquinone in carbon tetrachloride; some observations on the induced decomposition of the peroxide

The reaction between benzoyl peroxide and p-benzoquinone in CCl₄ was investigated by isolation and identification of the reaction products. At peroxide/quinone ratios ≥ 3 only quinonoid products of the spontaneous decomposition of the peroxide are formed. At ratios < 3 the peroxide undergoes induced decomposition by both trichloromethyl and phenyl radicals. The induced decomposition involves the formation of radical intermediates which undergo intermolecular disproportionation, but not intramolecular rearrangement to form p-trichloromethylbenzoyloxy radicals, p-phenylbenzoyloxy radicals, and their corresponding acids. The p-trichloromethylbenzoyloxy radicals are captured by benzoquinone to form 2-(p-trichloromethylbenzoyloxy)-1,4-benzoquinone and a considerable amount of quinonoid resins. A correlation between the electron-donating or accepting property of a radical and its capability to induce the decomposition of the peroxide was developed.     

Modellsubstanzen für polymere Redoxsysteme, 8. Tetra- und hexavalente Redoxsysteme vom 1,4-Benzochinon-Typus

The synthesis and properties of the following oligomeric redox systems are described: 2-(1,4-benzoquinone-2-ylmethyl)-5-methyl-1,4-benzoquinone ( 2b ), the three isomeric bis(1,4-benzoquinone-2-ylmethyl)benzenes 8a, 9a and 10a and their homologues, the isomeric bis[2-(1,4-benzoquinone-2-yl)ethyl]-benzenes 8b, 9b and 10b . By ¹H-NMR-spectroscopy the existence of 2-(2,5-dihydroxybenzyl)-1,4-benzoquinone ( 4 ) can be demonstrated, which reveals that in acidic solutions partly oxidized or reduced tetravalent redox systems of the quinone type molecules represent covalently bound quinone-hydroquinone systems. In contrast to the other compounds the partly reduced o-bis(quinone-2-yl) compound 8a easily forms an intramolecular charge-transfer complex in solution. The following totally symmetric hexavalent redox systems were synthesized as models for oxidation-reduction polymers: tris(1,4-benzoquinone-2-yl)methane ( 17 ), tris(1,4-benzo-quinone-2-ylmethy1)benzene ( 19a ), and tris[2-(1,4-benzoquinone-2-yl)ethyl] benzene ( 19b ).     

Synthesis of alternating polydepsipeptides by ring-opening polymerization of morpholine-2,5-dione derivatives

Polydepsipeptides with alternating α-hydroxy acid and α-amino acid residues were synthesized by ring-opening polymerization of morpholine-2,5-dione derivatives. The polymerizations were performed in the melt using stannous octoate as an initiator. Molecular weights of the polydepsipeptides obtained ranged from 0,9 · 10⁴ to 7,4 · 10⁴. Morpholine-2,5-dione derivatives unsubstituted at the 6-position gave polymers with the highest molecular weights. Poly((S)-alanine-alt-glycolic acid) was semi-crystalline, whereas all other polydepsipeptides synthesized were amorphous. Morpholine-2,5-dione derivatives were synthesized by N-acylation of glycine, (S)-alanine or (S)-valine with chloroacetyl chloride or (R,S)-2-bromopropionyl bromide, followed by ring-closure of N-(2-halogenacyl)-amino acid sodium salts in the melt in 4 to 83% yield. Low yields in the cyclization reaction of N-(2-halogenacyl)-(S)-valine were accompanied by the formation of the corresponding polydepsipeptides in 13 to 46% yield, with molecular weights ranging from 3,3 · 10⁴ to 4,9 · 10⁴.     

Number of active centers and propagation rate constants in the propene polymerization on supported Ti–Mg catalysts in the presence of hydrogen

Polymerization inhibition with radioactive carbon monoxide was used to determine the number of active centers (C_p) and the propagation rate constant (K_p) in the isospecific polymerization of propene with the catalytic system TiCl₄/diisobutyl phthalate/MgCl₂—AlEt₃—PhSi(OEt)₃. The presence of hydrogen was found to decrease C_p (by a factor of ≈ 2) and to increase k_p (by a factor of ≈ 4). In the absence of hydrogen a considerable part of the active centers (titanium-polymer bonds) reacting with ¹⁴CO seems to be inactive in the propene polymerization for steric reasons. Hydrogen is able to transform such centers into an active state. Thus, k_p ≈ 2,5 · 10³ L/(mol · s) at 70°C obtained in propene polymerization in the presence of the hydrogen seems to be correct, since the portion of centers in the active state is maximum. The influence of polymerization time, external and internal donors on C_p and k_p was studied.     

Synthesis and characterization of metal containing polychloranilamides

2,5-Diamino-3,6-dichloro-1,4-benzoquinone (chloranilamide) condensates, under generation of HCl, above 300°C to form polychloranilamide. The reaction was studied by thermovolumetric measurements, especially in the presence of different metal salts (cobalt, iron and manganese). The composition of the brittle black polymers is as expected, and the IR spectra resemble to those of the corresponding model compounds based on 5,8-dihydroxyquinoxaline. Their electrical conductivity is 10^?8 – 10^?5 S · cm^?1. Metal contents of up to 25 wt.-% were achieved corresponding to 80% of the theoretical value. The metal complexes are not stable against acids, and the compounds are not very resistant in a strongly alkaline milieu. Nevertheless, they could be promising, e.g., as ion exchangers, as precursors for organic materials with high metal contents such as catalysts, or as model compounds for similar polymers.     

Structure and physicochemical properties of the aldol and vinylene forms of poly(2,5-heteroarylenevinylene)s

We determined the structure and physicochemical properties of poly(2,5-furylenevinylene), poly(2,5-thienylenevinylene) and poly(2,5-furylene-co-2,5-thienylenevinylene) that were synthesized via aldol polycondensation. Two kinds of polymer were obtained, one with mainly aldol and one with mainly vinylene structure units. The former are soluble in water, and the latter insoluble in water and only slightly soluble in organic solvents. The aldol polymers can be transformed to vinylene polymers by thermal dehydration. The d.c. conductivities at room temperature are of the order of 10^?12 and 10^?8 S/cm for the aldol and vinylene forms, respectively.     

A novel synthetic route to rigid-rod polyimides

A new synthetic approach to soluble, rigid-rod, aromatic polymides is described. The polycondensation is done by a Pd-catalyzed aryl-aryl coupling of N,N′-bis(4-bromo-2,5-didodecyl-phenyl)-1,2:4,5-pyromellitic diimide ( 2 ) and 2,5-didodecyl-1,4-benzenediboronic acid ( 3 ). Here, the imide structure is already preformed in monomer 2 . A structurally identical polymer is synthesized by the classical procedure condensing 1,2:4,5-pyromellitic dianhydride (PMDA) ( 4 ) and 4,4″-diamino-2,5,2′,5′,2″,5″-hexadodecyl-p-terphenyl ( 5 ). Both polymers are characterized in detail by ¹H and ¹³C NMR spectroscopy, membrane osmometry and size exclusion chromatography. The average degree of polycondensation is of the order of 15. The thermal behaviour of the polymers is studied by differential scanning calorimetry and thermogravimetrical analysis.     

Polycarbonates and polyesters containing oxadiazole rings

Two new bisphenols containing an oxadiazole ring, 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole and 2,5-bis(m-hydroxyphenyl)-1,3,4-oxadiazole, were synthesized starting from p- and m-hydroxybenzoic acid and hydrazine. Polycarbonates having an inherent viscosity up to 0.5 were obtained by transesterification of the bisphenols with diphenyl carbonate. Similarly, aromatic polyesters were prepared from the corresponding diphenyl esters. These polycarbonates and polyesters were insoluble in all organic solvents, and indicated a high degree of crystallinity. The melting point of all the polymers containing oxadiazole rings were much higher than that of the polymers derived from bisphenol A.     

Electrochemical polymerization of derivatives from N-methylpyrrole and thiophene to heteroarylenevinylene polymers

The heteroaryl- and heteroarylenevinylene compounds 1, 2, 3 , and 4 were investigated by means of cyclic voltammetry and submitted to oxidative electropolymerization under galvanostatic conditions; the products obtained were further characterized by means of elemental analysis, optical absorption spectroscopy and conductivity measurements. (E)-1,2-bis(N-methyl-2-pyrrolyl)ethylene ( 1 ), 2,5-bis[(E)-2-(N-methyl-2-pyrrolyl)vinyl]thiophene ( 2 ) and N-methyl2,5-bis[(E)-2-(N-methyl-2-pyrrolyl)vinyl]pyrrole ( 3 ) gave brittle to spongy films on electropolymerization with perchlorate as the counterion balancing the positive charge on the polymer backbone units. The d. c. conductivity of all three polymers (as perchlorates) was of the order of 10^?3 Ω^?1·cm^?1. N-methyl-2,5-bis[(E)-2-(2-thienyl)vinyl]pyrrole ( 4 ) did not give a solid polymer.     

Studies on functional micelles, 4. Effect of alkyl chain length on the micellar reaction of thioalanine S-alkyl esters

S-Hexadecyl, S-dodecyl, S-decyl, and S-octyl esters of thioalanine ( 1e, 1d, 1c , and 1b ) were prepared and reacted at a concentration range of 2,5·10^?3 to 1·10^?1 mol/l in water with pyridine as a base catalyst to give the cyclic dimer of alanine, 3,6-dimethyl-2,5-piperazinedione ( 2 ). The yields of 2 from 1e and 1d were similar within this concentration range, whereas the yield of 2 from 1b rapidly decreased in the concentration range from 1·10^?1 to 1·10^?2 mol/l, and no dimer 2 was obtained at 2,5·10^?3 and 5·10^?3 mol/l. These results support the proposed micellar mechanism in the condensation of thioalanine S-alkyl esters in water.     

Autoxidation reactions of polystyrene derivatives

p-Isopropylstyrene was homopolymerized or copolymerized with styrene using AIBN as initiator in benzene at 50°C. The resulting polymers were easily oxidized by oxygen to produce polymers having hydroperoxy groups. The oxidized polymer was found to have considerably different solubility from the original polymer. Kinetic evaluation of the oxidation reactions of poly(p-isopropylstyrene) showed that the tertiary hydrogen of the isopropyl group present at the pendant aromatic ring was more susceptible to the oxidation reaction than the main chain methine hydrogen. The rate constants of these two oxidation reactions were found to be 4,0 · 10^?4 mol^?1/2 · l^1/2 · s^{Autoxidation reactions of polystyrene derivatives1/2} and 2,5 · 10^?4 mol^?1/2 · l^1/2 · s^?1/2, respectively. These values were much smaller than that for the tertiary hydrogen atom of the isopropyl group of cumene (3,21 · 10^?3 mol^?1/2 · l^1/2 · s^?1/2, at 68°C), a low molecular weight model compound.     

Aqueous polymerization of acrylamide initiated by acidic permanganate/thiourea redox system

The polymerization of acrylamide, initiated by acidic permanganate/thiourea redox system, was studied in aqueous media at 30 ± 0,2 °C in nitrogen. The rate of polymerization (R_p) was found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration, within the range of 0,5 · 10^?2 to 1,4 · 10^?2 mol dm^?3, and independent of the thiourea concentration. However, the rate of polymerization varies with the first power of the hydrochloric acid concentration within the range of 2,85 · 10^?2 to 11,4 · 10^?2 mol dm^?3, and increases linearly up to certain extent by varying the monomer concentration from 2,5 · 10^?2 to 12,5 · 10^?2 mol dm^?3. A deviation from the linear behaviour is observed, however, above a concentration of 12,5 · 10^?2 mol dm^?3. The initial rate of polymerization (R_i) as well as the maximum conversion increases by increasing the temperature up to 35 °C, but the maximum conversion falls as the temperature rises above 35 °C. The overall energy of activation is found to be 47,70 kJ mol^?1 (11,48 kcal/mol^?1) within the temperature range of 25–45 °C. Addition of salts, except manganous salts, was found to be associated with a depression in the R_p and maximum conversion. The effect of cationic and anionic surfactants has been found to increase and decrease the R_p respectively; non-ionic detergents, however, have no effect on the R_p.