Swelling ratio driven changes of probe concentration in pH- and ionic strength-sensitive poly(acrylic acid) hydrogels

Poly(acrylic acid) gels are known to swell to different extent (measured by the swelling ratio) depending on pH and ionic strength of the solution. The experimental method employed by us to monitor the concentration and diffusion coefficient of the probes allows the simultaneous determination of their concentration and diffusion coefficient for any value of the ionic strength and pH of the solution trapped in the polymeric network. Two different electroactive probe systems, 1,1′-ferrocenedimethanol and 2,2,6,6-tetramethylpiperidine 1-oxyl, were selected for the examination. Small values of the swelling ratio, obtained either by application of a high ionic strength or a low pH, result in an unexpected high concentration of both probes in the gel samples. Correspondingly, the probes diffusion coefficients were much smaller compared to their values in the swollen gels.     

The effect of aliovalent impurities on the sulfidation kinetics of manganese and molybdenum

The influence of aliovalent impurities on the kinetics and mechanism of manganese and molybdenum sulfidation has been demonstrated, as a function of temperature (1,073–1,273 K) and sulfur pressure (1–10⁴ Pa). The results of these experiments have been considered in terms of Hauffe–Wagner theory of doping, which made it possible to explain the different influence of aliovalent impurities on the sulfidation kinetics of manganese and molybdenum. It has been shown that the same impurity may play both the positive or negative role in the corrosion behavior of a given metal and it is not possible to predict the type of this influence without the detailed knowledge of point defect structure of sulfide or oxide scales and, in particular, of the mechanism of impurity dissolution in the crystallographic structure of oxidation or sulfidation products.     

Polymer Composites Based on Reactive Carboxylate-Alumoxanes

Summary: The possibility of applying basic aluminum carboxylates as the cross-linking monomers in radical polymerization processes as well as the initiators for ATRP of styrene and coordination ROP of heterocyclic monomers was examined. It was established, that aluminum carboxylates containing in their structure the acrylic and lauric acids derivatives show high activity in the copolymerization with vinyl monomers which results in the hybrid polymer networks formation. In the typical ATRP conditions, polymers grafted with styrene are obtained while basic aluminum 2-bromopropionate is used as the initiator. Hybrid composites i.e. core-shell nanospheres can be obtained in this way at low degree of polymerization. Nanoparticles of basic aluminum caroboxylates when reacted with triethylaluminum show high activity as initiators in the polymerization processes of ε-caprolactone, trimethylene carbonate as well as propylene and ethylene oxides. Cross-linked products in the form of a gel were formed as the result of ROP in such systems. However, linear polymers characterized by M_n above 10⁴ and PDI ≥ 1.9 were obtained after aluminum residuals removal.     

Local mobility in grafted polydimethylsiloxane melts

Spin–lattice relaxation time constants, T₁, were studied for low-molecular-weight linear and grafted polydimethylsiloxane over a wide temperature and frequency range. Quantitative evaluations of proton T₁ measurements indicated two relaxation processes: anisotropic rotation of methyl groups around the Si–C bond (low temperature process) and motions of the PDMS side-chains connected with the glass transition (high temperature process). Additional analyses of the T₁ relaxation dispersion profiles revealed specific local segment fluctuation times, which are characteristic of the coherent motions in the grafted polymer chains.     

3‐P⩵O‐Functionalized Phospholane 1‐Oxides by the Michael Reaction of 1‐Phenyl‐2‐phospholene 1‐Oxide and Dialkyl Phosphites,H‐Phosphinates,or Diphenylphosphine Oxide

The addition of dialkyl phosphites, H‐phosphinates, and diphenylphosphine oxide on the β carbon atom of the not too reactive double bond of 1‐phenyl‐2‐phospholene 1‐oxide was carried out in two ways. According to the first approach (A), the P‐reagents were activated by trimethylaluminum prior to the Michael addition. The second method (B) involved the microwave(MW)‐assisted solventless reaction of the P‐species with the phospholene oxide. In general, method A was more efficient and more selective than route B. However, the addition of dialkyl phosphites and diphenylphosphine oxide could also be accomplished well under MW conditions. The disadvantage of the MW‐assisted approach is that the Michael adducts are formed as a mixture of isomers. The 3‐P⩵O‐phospholane oxides are novel products, and among these, the bis(phosphine oxide) is the precursor of the bidentate P‐ligand LuPhos.     

The Hydrogen–Deuterium Exchange at α-Carbon Atom in <Emphasis Type="BoldItalic">N,N,N</Emphasis>-Trialkylglycine Residue: ESI-MS Studies

Derivatization of peptides as quaternary ammonium salts (QAS) is a known method for sensitive detection by electrospray ionization tandem mass spectrometry. Hydrogens at α-carbon atom in N,N,N-trialkylglycine residue can be easily exchanged by deuterons. The exchange reaction is base-catalyzed and is dramatically slow at lower pH. Introduced deuterons are stable in acidic aqueous solution and are not back-exchanged during LC-MS analysis. Increased ionization efficiency, provided by the fixed positive charge on QAS group, as well as the deuterium labeling, enables the analysis of trace amounts of peptides.     

Construction of a porous homochiral coordination polymer with two types of Cu(n)I(n) alternating units linked by quinine: a solvothermal and a mechanochemical approach

The polymer network: The reaction of quinine (QN) with CuI under solvothermal, as well as liquid-assisted grinding, conditions afforded a unique 1D homochiral coordination polymer {[Cu(4)(μ(3)-I)(4)(QN)(2)][Cu(3)(μ(3)-I)(2)(μ(2)-I)(QN)(2)](2)}(n), containing both triangular Cu(3)I(3) and cubane Cu(4)I(4) clusters as connecting nodes (see scheme). Van der Waals interactions between the adjacent 1D polymer chains lead to an extended quasi-honeycomb homochiral pillared 3D network with solvent-free 1D channels.     

Influence of temperature and interactions with ligands on dissociation of dsDNA and ligand-dsDNA complexes of various types of binding. An electrochemical study

Several medicinally important compounds that bind to dsDNA strands via intercalation (C-1311, C-1305, EtBr), major groove binding (Hoechst 33258) and covalent binding (cis-Pt) were examined. The obtained results suggest that both the transfer of conformation B to C and the denaturation process, for the ligand-dsDNA complexes, except for covalently bound cis-Pt, took place at higher temperatures compared to the unbound helix. Furthermore, much lower currents of electrooxidation of guanine at 100 °C, compared to the currents obtained at this temperature for dsDNA in the absence of ligands, suggest that the binding of ligands affects the way the dsDNA denaturates at increased temperatures and leads to formation of different forms of DNA single strands. The voltammetric results were compared with the data of two spectroscopic techniques: UV-Vis and CD.     

Emulsion chamber observations of Centauros,aligned events and the long-flying component

The cosmic ray emulsion chamber community has reported several unusual phenomena which are also relevant to experiments at the current high-energy accelerators, in particular the Fermilab Tevatron Collider and the CERN Large Hadron Collider (LHC). A summary of the ”Cosmic Rays at Mountain Altitude” workshop held at Plock (Poland, September 2010) is given.     

On the measurability of functions with quasi-continuous and upper semi-continuous vertical sections

Let f: ?² → ? be a function with upper semicontinuous and quasi-continuous vertical sections f _x (t) = f(x, t), t, x ∈ ?. It is proved that if the horizontal sections f ^y (t) = f(t, y), y, t ∈ ?, are of Baire class α (resp. Lebesgue measurable) [resp. with the Baire property] then f is of Baire class α + 2 (resp. Lebesgue measurable and sup-measurable) [resp. has Baire property].