Mikhail G. Zolotukhin

Remarkable enhancement of reactivity of carbonyl compounds for polymerizations with non-activated aromatic hydrocarbons

Reaction of carbonyl compounds bearing electron-withdrawing substituents with non-activated aromatic hydrocarbons proceeds selectively in trifluoromethanesulfonic acid (TFSA) at room temperature to give linear, high-molecular-weight polymers.

Light Emission Properties of a Cross-Conjugated Fluorene Polymer: Demonstration of Its Use in Electro-Luminescence and Lasing Devices

Light emission properties of a fluorene cross-conjugated polymer (PF–1) based on the monomer 4,7-bis[2-(9,9-dimethyl)fluorenyl] benzo[1,2,5]thiadiazole are reported. This polymer exhibits solubility at high concentrations, good processability into thin solid films of good quality and a broad emission band with a fluorescence quantum yield of approximately 1. Based on these features, in this paper we implemented the use of PF–1 as an active layer in polymer light-emitting diodes (PLEDs) and as a laser gain medium in solution. To get insight on the conducting properties of PF–1, two different electron injectors, poly [(9,9-bis(3′-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)] (PFN) and lithium fluoride (LiF), were used in a simple PLED architecture. PLEDs with the PFN film were found to exhibit better performance with a maximum luminous efficiency of 40 cd/A, a turn-on voltage (Von) of approximately 4.5 V and a luminance maximum of 878 cd/m2 at 5.5 V, with a current density of 20 A/m2. For the lasing properties of PF–1, we found a lasing threshold of around 75 μJ and a tunability of 20 nm. These values are comparable with those of rhodamine 6G, a well-known laser dye.

Reactions of ketones with aromatics in acid media. The effect of trifluoromethyl groups and the acidity media. A theoretical study

AbstractThe reactions of acetone, 2,2,2-trifluoroacetone and hexafluoroacetone in methanesulfonic (MSA) and triflic acids (TFSA) with benzene have been studied at M06-2X/6-311+G(d,p) level using cluster-continuum model, where the carbonyl group is explicitly solvated by acid molecules. The introduction of a trifluoromethyl group into the ketone structure reduces the activation energy of the tetrahedral intermediates formation due to an increase of the electrophilicity of the carbonyl group and raises the activation and the reaction energies of the C-O bond cleavage in formed carbinol due to the destabilization of the corresponding carbocation. The introduction of the second trifluoromethyl group inhibits the hydroxyalkylation reaction due to a very strong increase of the reaction and activation energies of the C-O bond cleavage which becomes the rate determining step. The most important catalytic effect of TFSA compared to MSA is not the protonation of the ketone carbonyl, but the reduction of the activation and reaction energies of the carbinol C-O bond cleavage due to better protosolvation properties. Even for TFSA no complete proton transfer to carbonyl oxygen has been observed for free ketones. Therefore, the protonation energies of free ketones cannot be considered as a measure of ketone reactivity in the hydroxyalkylation reaction. FigureReactions of ketones with aromatics in acid media 

Oligomerization of 3,5-dimethyl benzyl alcohol promoted by clay: experimental and theoretical study.

Linear oligomerization of 3,5-dimethyl benzyl alcohol is induced by a montmorillonite clay (Tonsil Optimum Extra), producing 1,3,5,7-tetramethyl-9,10-dihydro-anthracene, which, by loss of protons results in the product 1,3,5,7-tetramethylanthracene. It was also found that the compounds 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetramethyl-9,10-dihydroanthracece and 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetra-methylanthracene were formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene. 1,3,5,7-Tetramethylanthryl radical cation was formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene; it was characterized by Electronic Paramagnetic Resonance (EPR). On the other hand, a theoretical analysis was performed, allowing the rationalization of the observed products and some of the key reaction steps.

Mechanistic aspects of superacid mediated condensation of polyphenols with ketones. Implications for polymer synthesis.

A detailed computational study of possible reaction paths for methanesulfonic and triflic acid mediated polyhydroxyalkylation reaction between resorcinol and trifluoracetone accompanied by cyclodehydration to give 9H-xanthene containing polymers has been carried out at M06-2X/6-311+G** level of theory. A cluster solvation model was used for the calculations. The calculations revealed that the most kinetically favorable reaction path involves the cyclodehydration occurring during the polymer forming step. In this case 9H-xanthene formation is promoted by the activated phenyl ring in Wheland intermediate assisting the aromatic nucleophilic substitution of OH group which leads to the cyclization. It has been demonstrated that the inability of methanesulfonic acid to catalyze the formation of 9H-xanthene containing polymers is due to the very high barrier of the rate limiting step of the polymer forming reaction and not the cyclodehydration process.

A Novel Approach to the Synthesis of High Performance and Functional Polymers

A novel series of linear, high molecular weight high performance and functional polymers were synthesized by a one-pot, superacid-catalyzed polyhydroxylakylation reaction of carbonyl compounds containing electron-withdrawing substituents, adjacent or relatively close to a carbocation center with non-activated aromatic hydrocarbons. The reactions were performed at room temperature in the Brønsted superacid CF3SO3H (trifluoromethanesulfonic acid, TFSA) and in a mixture of TFSA with methylene chloride, which was used as both solvent and a medium for generation of electrophilic species from the carbonyl component. Polycondensations of 1,1,1-trifluoroacetone, 2,2,2-trifluoroacetohenone, 2,7-dinitrofluorenone, acenaphthenequinone and isatin with aromatic hydrocarbons proceed readily in the presence of superacid at room temperature. The polymers obtained were found to be soluble in the common organic solvents, and flexible transparent films could be cast from the solutions. 1H and 13C NMR analyses of the polymers synthesized revealed their linear, highly regular structure. The polymers also possess high thermostability.

OLEDs fabricated by solution process based on a novel linear poly(arylene oxindole)

In this work, OLEDs based on a new modified polymer PMC 300* (as emissive layer: EML) were manufactured with the structure ITO/PEDOT:PSS/Polymer (PMC 300*)/LiF or PFN/Al. This new polymer PMC 300*: Poly[(Benzo[c][1,2,5]thiadiazole-4,7-diylbis(9,9-dimethyl-9H-fluorene-7,2-diyl))-3,3-diyl(1-(3- (trifluoromethyl)phenyl)-2-oxindole)], is a modified version of PF-1 polymer that was synthesized and used previously in our group for non-linear optical properties and in OLED devices. The CF3 additional group on PMC 300* showed an improved electroluminescence and current efficiency on OLED devices. PF-1 and PMC 300* polymers have a fluorescence quantum yield (FLQY) of approximately 1. Film formation of the hole injection layer (HIL) and the EML were made by spin coating and subsequently evaporating LiF (or PFN by spin coating) and Al as cathode. Polymer films show a very low roughness (~ 1-2 nm), as most of the polymers used in OLEDs. Due to PMC 300* excellent properties like high solubility, very high QY, high conjugation and mechanical characteristics, OLEDs based on this new modified polymer (with emission in green-yellow wavelengths) showed luminances up to 1937 cd/m2, high current efficiencies of 35 cd/A and a maximum external quantum efficiency (EQEmax) of 2.6 %. Additionally, preliminary tests of flexible OLEDs by using this polymer are currently carrying out, results are promising.

Comparison of the structure and thermal properties of a poly(aryl ether ketone ether ketone naphthyl ketone) with those of poly(aryl ether ketone ether ketone ketone)

Abstract Poly(oxy-1,4-phenylene carbonyl-1,4-phenylene oxy-1,4-phenylene carbonyl-2,6-naphthalene carbonyl-1,4-phenylene) or 2,6-PEKEKNK is a polymer of the poly(aryl ether ketone) family differing from PEKEKK by the presence of a naphthyl group linked at positions 2 and 6 to the two ketone groups. It is synthesized by electrophilic precipitation polycondensation of 2,6- naphthalenedicarboxylic acid chloride with 4,4’-bis-(4-phenoxy) benzophenone in the presence of aluminium chloride. The dimensions of the orthorhombic unit cell determined from an initially amorphous, stretched film are: a = 0.778 nm, b = 0.613 nm, c = 5.52 nm. In contrast with PEKEKK no signs of polymorphism were found for 2,6 PEKEKNK. Its glass transition and melting temperatures are 20 °C and 2 °C above those of PEKEKK, respectively.

Electroluminescence of poly(phthalidylidene arylene)s

Electroluminescence of thin films of poly(3,3-phthalidylidene-4,4′-biphenylylene) (PPB) and poly(3,3-phthalidylidene-2,7-fluorenylylene) (PPF) was studied. In both cases, electroluminescene was found to be of a threshold origin. Emission maxima and quantum efficiencies for PPB and PPF are 490 and 525 nm, 0.01 and 0.1%, respectively. The electroluminescent characteristics were found to be strongly dependent on the polymer used. Die Elektrochemilumineszenz von dunnen Poly(3,3-phthalidyliden-4,4′-biphenylylen) (PPB) und Poly(3,3-phthalidyliden-2,7-fluorenylylen)-Filmen (PPF) wurde untersucht. Es wird gezeigt, das in beiden Fallen die Elektrochemilumineszenz bei bestimmten Spannungswerten beginnt, die hoher sind als die Schwellenspannungswerte. Die Maximalemissionen sowie die Quanteneffektivitaten der Elektrochemilumineszenz fur PPB und PPF betragen 490 und 525 nm bzw. 0,01 und 0,1%. Die Chemilumineszenzparameter hangen stark vom Polymertyp ab.

Poly(Phthalidylidenearylene)S. Transformation of poly(3,3-phthalidylidene-4,4′-biphenylene) in acidic media

The behaviour of poly(3,3-phthalidylidene-4,4′-biphenylylene) (PPB) in acidic media was studied. In solvents with high acidity e.g. concentrated sulfuric acid, chlorosulfonic acid or PCl5, the phthalide groups of PPB were transformed into anthracen-9-one groups. Exposure time, solvent and temperature were found to affect the rearrangement of 3,3-diphenylphthalide and PPB in the presence of PCl5. The resulted polymers are soluble in common organic solvents and contain either 10-chloro-10-aryl-anthracen-9-one, or after hydrolysis, 10-hydroxy-10-arylanthracen-9-one units. Flexible and transparent polymer films were prepared by casting from the solution.