Environment‐Adopting Surfaces with Reversibly Switchable Morphology

Two‐component polymer brushes (polystyrene and poly(2‐vinylpyridine)) were synthesized by grafting from the surface of Si‐wafers. The brushes are sensitive to the surrounding medium, and their morphology and composition of the top of a brush can be switched upon exposure to different solvents. Thus surface energetic states and roughness of the film can be precisely tuned.     

The Spider Paracoelotes birulai: Detection and Structure Elucidation of New Acylpolyamines by On‐Line Coupled HPLC‐APCI‐MS and HPLC‐APCI‐MS/MS

The lyophilized venom of the spider Paracoelotes birulai (Araneidae: Amaurobiidae) has been analyzed. A number of acylpolyamines were found and separated. By on‐line coupled high‐performance liquid chromatography and atmospheric‐pressure chemical‐ionization mass spectrometry, the structures of the three most abundant compounds PB 490 (N‐(16‐guanidino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxyindol‐3‐yl)acetamide; Fig. 3, b), PB 421 (N‐(16‐guanidino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxybenzamide; Fig. 4, a), and PB 448 (N‐(16‐amino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxyindol‐3‐yl)acetamide; Fig. 5,b) were elucidated. Two different types of polyamines were found in the α‐palutoxins and compared with acylpolyamines from the Agelenidae spider family. The results of this investigation will initiate further chemotaxonomical studies on spiders.     

Oscillatory phenomena at polyvinylpyridine/silica interfaces

Oscillations of the aggregate sizes of SiO₂ particles covered by an adsorbed layer of poly(vinylpyridine) (PVP) at pH 3 with a periodicity of about 15 h were observed using a particle counting technique. The same oscillation was found for the contact angle values of water on the surface of Si wafers (with top silica layer) covered by adsorbed PVP as a function of exposure time in a PVP water solution.     

Effect of nano-carbon dispersions on signal in silicon-based sensor structure with photoelectrical transducer principle

We identified different nano-carbon species such as graphene nanoplatelets, graphite flakes and carbon nanotubes dispersed in N-methyl-2-pyrrolidone using a novel sensor structure based on a “deep” silicon barrier working as a photoelectrical transducer. Each nano-carbon particle has specific signature in both 2D photocurrent distribution and photocurrent dependencies on bias changing surface band-bending. Additionally, all nano-carbon particles have characteristic features in the time-dependent evolution of photocurrent. The obtained results can be explained by the influence of nano-carbon molecules' local electric field on the recombination parameters of defect centers on the silicon surface.     

Oxidation and chlorination reactions of perfluoroketene-N,S-acetals

The paper presents the results of the investigation of oxidation and chlorination reactions of perfluoroketene-N,S-acetals. Oxidation reactions of perfluoroketene-N,S-acetals proved to be dependent on the nature of oxidizing agent and led to the formation of corresponding sulfone in the case of m-chloroperbenzoic acid or amides of α-H-perfluoroalkane carboxylic acids in the case of tert-butyl hydroperoxide or hydrogen peroxide. Reaction of 1-tert-butylsulfanyl-2,3,3,4,4,4-hexafluoro-1-[N-methyl,N-((S)-α-methylbenzyl)amino]-but-1-ene with sulfuryl chloride demonstrated the chlorination of perfluoroketene-N,S-acetals as a new approach in the synthesis of chiral α-chloro perfluoroalkane carboxylic acid amides.     

Darwin and mass-velocity relativistic corrections in non-Born-Oppenheimer variational calculations

The Pauli approach to account for the mass-velocity and Darwin relativistic corrections has been applied to the formalism for quantum mechanical molecular calculations that does not assume the Born-Oppenheimer (BO) approximation regarding separability of the electronic and nuclear motions in molecular systems. The corrections are determined using the first order perturbation theory and are derived for the non-BO wave function of a diatomic system expressed in terms of explicitly correlated Gaussian functions with premultipliers in the form of even powers of the internuclear distance. As a numerical example we used calculations of the transition energies for pure vibrational states of the HD(+) ion.     

Synthesis of 2,3-trans disubstituted tetrahydrofurans through sequential xanthate radical addition-substitution reactions

A two-step preparation of 2,3-trans disubstituted tetrahydrofuran derivatives is reported from S-alkyl dithiocarbonates. The study of the group transfer reaction from xanthates and alkenes afforded intermediate S-alkyl dithiocarbonates. From 2,3-dihydrofuran derivatives, the displacement of the resulting anomeric xanthates with various nucleophiles in the presence of Lewis acid allowed the formation of new carbon-carbon and carbon-heteroatom bonds. This strategy was illustrated by a two-step synthesis of a precursor of modified 2'-beta-C-branched nucleoside analogues.     

The question of aromaticity in open-shell cations and anions as ion-radical offsprings of polycyclic aromatic and antiaromatic hydrocarbons

Arene cation-radicals and anion-radicals result directly from the one-electron oxidation and reduction of many aromatic hydrocarbons, yet virtually nothing is known of their intrinsic (thermodynamic) stability and hence "aromatic character". Since such paramagnetic ion radicals lie intermediate between aromatic (Hückel) hydrocarbons with 4n + 2-electrons and antiaromatic analogues with 4n-electrons, we can now address the question of pi-delocalization in these odd-electron counterparts. Application of the structure-based "harmonic oscillator model of aromaticity" or the HOMA method leads to the surprising conclusion that the aromaticity of these rather reactive, kinetically unstable arene cation and anion radicals (as measured by the HOMA index) is actually higher than that of their (diamagnetic) parent-contrary to conventional expectations.     

Formation of Polymer Nanolayers with Special Properties at Polymer Surfaces

A principal possibility of the utilization of polymer peroxides for the modification of polymer surfaces that provides an immobilization of the tailored quantity of peroxide groups at them has been established. The processes of polymer surface activation with following “grafting from” or “grafting to” utilizing immobilized peroxide groups has been studied using a FTIR-ATR spectroscopy, ellipsometry and measurements of contact angles. The proposed technique of polymer surface activation is based on the universal ability of carbon chain polymer to participate the free radical reactions.