Gintaras Buika

Polymerization of 9-(2,3-epoxypropyl)carbazole with complexes of potassium compounds and 18-crown-6

Abstract Homogeneous anionic polymerization of 9-(2,3-epoxypropyl)carbazole (EPC) initiated by the complex of 18-crown-6 with potassium hydroxide, potassium acetate or potassium benzoate was carried out in toluene. These catalytic systems allowed polymerization of EPC at low temperature, leading to oligomers of a relatively wide range of molecular weight. Dependence of duration of the induction period and of initial polymerization rate on the catalytic system have been observed. The catalytic system also strongly influences the occurrence of chain transfer reactions. Differences in chain transfer constant have been explained by the different basicities of the active centres.

The thermal degradation of copolymers of carbazolylethyl(meth)acrylates and methacrylic acid

The thermal degradation of the (co)polymers of 2-(9-carbazolyl)ethyl methacrylate and 2-(9-carbazolyl)ethyl acrylate with methacrylic acid was studied by thermogravimetry and differential thermal analysis. It was established that the thermal stability of the copolymers is higher than that of the corresponding homopolymers. The degradation of copolymers in which the content of methacrylic acid units is high was found to occur in two stages. One-stage degradation was observed for copolymers in which the amount of methacrylic acid units is lower than 80 mol percent. The formation of intramolecular and intermolecular anhydrides was observed in the thermal degradation of all of the copolymers.

Study on the initiation step of 2-(9-carbazolyl)ethyl glycidyl ether polymerization by K−, K+ (15-crown-5)2

Abstract Several reactions occur during the initiation of 2-(9-carbazolyl)ethyl glycidyl ether polymerization by K−, K+ (15-crown-5)2. At first the oxirane ring is opened mainly in the β-position. An organometallic intermediate obtained cleaved then the linear ether bond in the substituent and the cyclic one in crown ether. Various potassium alkoxides are finally formed. They are the real initiators of the polymerization. 9-Vinylcarbazole being another reaction product is inactive in this process.

Fluorescence properties of carbazolyl-containing amphiphilic copolymers

Abstract Amphiphilic random copolymers of 2-(9-carbazolyl)-1-methylethyl methacrylate, 2-(9-carbazolyl)ethyl methacrylate or 2-(9-carbazolyl)ethyl acrylate with methacrylic acid were synthesized and their fluorescence properties in aqueous solution were examined. The fluorescence spectra of the copolymers showed monomeric emission. The fluorescence intensity decreased with increase of the content of carbazolyl groups in the copolymers, indicating that some excited-state quenching occurs in these systems. The fluorescence intensity of the copolymers also changed with the change of pH of the solutions. The character of these changes was dependent on the content of carbazole chromophores in the copolymer. Solubilization of 8-anilino-1-naphthalenesulfonic acid ammonium salt and perylene by the copolymers synthesized has been studied. The energy transfer to hydrophobically-bound perylene was facilitated for carbazolylalkylmethacrylate copolymers when compared to that observed for carbazolylalkylacrylate copolymers.

Synthesis and cationic polymerization of 5-(2,3-epoxypropyl)amino-2-phenyl-1,2,3-benzotriazole

Abstract Synthesis and cationic polymerization of the new monomer 5-(2,3-epoxypropyl)amino-2-phenyl-1,2,3-benzotriazole (EAPB) is reported. The monomer was prepared either in the reaction of 5-amino-2-phenyl-1,2,3-benzotriazole with 1-chloro-2,3-epoxypropane or by the treatment of 5-(3-chloro-2-hydroxypropyl)amino-2-phenyl-1,2,3-benzotriazole with sodium hydroxide. Polymerization of EAPB with boron trifluoride diethyl etherate yielded the oligomers with the average degree of polymerization of 4–5. The limit conversion of the monomer did not exceed 53%. The introduction of 1,2-ethane diol into the reaction mixture led to the higher yield of the oligomer. Investigation of polymerization of EAPB by GPC and microcalorimetry as well as analysis of the resulting oligomers by IR spectrometry has shown that, in the presence of 1,2-ethanediol, the reaction proceeds by an activated monomer mechanism, whereas in the absence of the diol, it proceeds by the conventional active chain end mechanism.

Electron-transfer processes in the reaction of K−, K+(15-crown-5)2 with carbazole: unexpected formation of metallic potassium

Abstract Transfer of one electron from K − to the aromatic ring occurs in the reaction of K − , K + (15-crown-5) 2 with carbazole giving K° and a radical anion. The latter rapidly decomposes with the liberation of hydrogen and formation of carbazylpotassium. It can also undergo an intramolecular proton-exchange reaction followed by a transfer of the second electron from the part of K° product. That leads to a dianion which then reacts with another carbazole molecule. Finally, carbazylpotassium and 1,4-dihydrocarbazylpotassium are formed.

Cationic photopolymerization of carbazolyl-containing vinyl ethers

Abstract Photopolymerizations of 2-(9-carbazolyl) ethyl vinyl ether (CEVE) and (9-carbazolyl) methoxy ethyl vinyl ether (CMEVE) initiated with diphenyl iodonium tetrafluoroborate (DPIT), di( tert -butylphenyl)iodonium tetrafluoroborate (BPIT), cyclopropyldiphenylsulfonium tetrafluoroborate (CPS) and (η 5 -2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6-η)-(1-methyl ethyl) benzene]-iron (+)-hexafluorophosphate(-1) (I261) were studied. It was established that the efficiency of the iodonium salts and iron–arene complex is much higher in the cationic photopolymerization of the monomers than that of the sulfonium salt. CMEVE showed higher reactivity in cationic photopolymerization than CEVE. Higher degrees of polymerization were established for the products CEVE photopolymerization compared with those of the products of CMEVE reaction. The influence of the temperature on the rate of CEVE and CMEVE photopolymerization, molecular weight and conversion limit is discussed.

Synthesis and Properties of the Derivatives of 2,4,6-Tris(Phenoxy)-1,3,5-Triazine

Five derivatives of 2,4,6-tris(phenoxy)-1,3,5-triazine were synthesized and characterized by 1H NMR, IR and mass spectrometries. The optical and electrochemical properties of the synthesized compounds were studied. Dilute solutions of 1,3,5-triazines compounds in acetonitrile absorb electromagnetic radiation in the region of 200-400 nm with the band gaps of 3.96–4.58 eV. Cyclic voltammetry studies revealed that the electron affinities of the synthesized compound range from −3.24 eV to −3.58 eV, and solid state ionization potentials range from 7.20 eV to 8.16 eV.

New Thiophene-Based Glass-Forming Hydrazones for Optoelectronic Applications

A new series of thiophene-containing glass-forming hydrazones is synthesized. The thermal, photoelectrical, and optical properties of these compounds are examined. The synthesized hydrazones exhibit the thermal stability sufficient for their application in optoelectronic devices. The values of ionization potential of amorphous films of the newly synthesized hydrazones are from 4.43 to 5.79 eV. The hole drift mobilities measured by the xerographic time-of-flight method in a molecularly doped polymer containing 50 wt.% of one synthesized hydrazone exceed 10−6 cm2/Vs at an electric field intensity of 6.4 × 10−5 V cm−1.

New carbazole-indan-1,3-dione- based host materials for phosphorescent organic light emitting diodes

ABSTRACT New carbazole- and indan-1,3-dione -based low molecular weight derivatives were synthesized and characterized by mass spectrometry and 1H NMR spectroscopy. Thermal behaviour of the derivatives was demonstrated by thermo-gravimetric analysis and differential scanning calorimetry. The materials were found to show very high thermal stability having initial thermal degradation temperatures in the range of 398- 401°C. Glass transition temperatures of the amorphous molecular materials were in the rage of 80–114°C. The derivatives were tested as host materials in blue phosphorescent organic light emitting diodes with iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate as the guests. One of the blue OLED devices demonstrated rather low turn-on voltage of 5.0 V, a maximum luminance efficiency of 2.73 cd/A and maximum brightness of about 220 cd/m2.