Cellulose‐based graft copolymers with controlled architecture prepared in a homogeneous phase

Cellulose‐based macroinitiators with predetermined number of initiation sites were synthesized by acylation of microcrystalline cellulose AVICEL PH‐101 with 2‐bromoisobutyryl bromide under homogeneous reaction conditions in the N,N‐dimethylacetamide/LiCl solvent system. The influence of different methods of cellulose activation on acylation efficiency and reproducibility was investigated. Best results were obtained using thermal activation under reduced pressure or the newly introduced protocol based on solvent exchange to 1,4‐dioxane. Prepared macroinitiators were used for grafting with styrene and methyl methacrylate (MMA) using optimized atom transfer radical polymerization reaction conditions to achieve well‐controlled polymerizations with high initiation efficiency. For MMA grafting, the initiation efficiency was shown to be dependent on certain reaction conditions, such as type of solvent, monomer concentration, or the presence of a sacrificial initiator. In addition, single‐electron transfer living radical polymerization with Cu(0) as the catalyst was used for the first time to prepare cellulose‐graft‐polystyrene and cellulose‐graft‐poly(MMA) copolymers in a homogeneous phase. In summary, homogeneous reaction conditions, stoichiometric control in the preparation of macroinitiators, and controlled grafting jointly allowed for an extensive control of copolymers architecture, that is, density of grafting, composition, and molecular parameters of grafts. Moreover, some of the prepared copolymers were characterized by static and dynamic light scattering and microscopic techniques (transmission electron microscopy and atomic force microscopy). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Accurate determination of Be magnetic moment

The determination of the magnetic moment of ⁹Be from the measured ratio of the nuclear to the electron g-factors g_I/g_J in ⁹Be⁺ is presented. The obtained result μ(⁹Be)=-1.17743159(3)μ_N is two orders of magnitude more accurate than the presently accepted value.     

Statefinders and observational measurement of superenergy

The superenergy of the universe is a tensorial quantity and it is a general relativistic analogue of the Appell's energy of acceleration in classical mechanics. We propose the way to measure this quantity by the application of the observational parameters such as the Hubble parameter, the deceleration parameter, the jerk and the snap (kerk), known as statefinders. We show that the superenergy of gravity requires only the Hubble and deceleration parameters to be measured, while the superenergy of matter requires also the measurement of the higher-order characteristics of expansion: the jerk and the snap. In such a way, the superenergy becomes another parameter characterizing the evolution of the universe. One of the interesting points is that the cosmological constant has a purely gravitational interpretation in terms of superenergy.     

A study of selected phytoestrogens retention by reverse osmosis and nanofiltration membranes - the role of fouling and scaling

Fouling and scaling are common phenomena that accompany membrane filtration and are caused by the presence of organic and inorganic matter in water, which may affect the removal of low-molecular mass organic micropollutants. Comparative filtration of deionized water containing selected phytoestrogens (biochanin A, daidzein, genistein, and coumestrol) was carried out using one new membrane and one contaminated with organic or inorganic matter. Two commercial Osmonics DS membranes were selected for the research, reverse osmosis DS3SE and nanofiltration DS5DK. Filtration was carried out in the dead-end mode. Higher removal of phytoestrogens was caused by reverse osmosis and retention depended on the molar mass of the compound. The decrease in membrane efficiency associated with fouling or scaling brings about an increase in the retention coefficient of phytoestrogens during both reverse osmosis and nanofiltration. The highest increase in phytoestrogen retention was found for the nanofiltraton membrane which was more susceptible to fouling than the osmotic one. This confirms the effect of membrane porosity on the phenomenon studied. The increase in micropollutants removal observed after fouling or scaling was caused by the modification of the membrane surface, hindered diffusion of the compound, and intensified or limited adsorption of micropollutants on the membrane surface.     

A mechanistic study on the fragmentation of peptide‐derived Amadori products

Gas phase fragmentation of peptide‐derived Amadori products was investigated using synthetic compounds regioselectively deuterated as well as labeled with ¹⁸O at aminofructose moiety. The eliminated molecule CH₂O contains exclusively protons attached to carbon C6 of the aminofructose moiety. The hydrogen atoms connected with the carbon C1 of the aminofructose moiety are partially eliminated as a component of water molecules during the dehydration process and partially dislocated within the fragmented peptide molecule. The labeled oxygen atom attached to the carbon C2 is eliminated in 100% along with the first loss of water. The MS³ experiments revealed that the product ion formed by triple dehydration of the Amadori product does not eliminate the formaldehyde molecule. On the basis of these observations we proposed a hypothetical mechanism of Amadori products' fragmentation. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct products of automorphism groups of graphs

In this article we study the product action of the direct product of automorphism groups of graphs. We generalize the results of Watkins [J. Combin Theory 11 (1971), 95–104], Nowitz and Watkins [Monatsh. Math. 76 (1972), 168–171] and W. Imrich [Israel J. Math. 11 (1972), 258–264], and we show that except for an infinite family of groups S_n × S_n, n≥2 and three other groups D₄ × S₂, D₄ × D₄ and S₄ × S₂ × S₂, the direct product of automorphism groups of two graphs is itself the automorphism group of a graph. © 2009 Wiley Periodicals, Inc. J Graph Theory 62: 26–36, 2009     

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.     

Optical acetylcholine sensor based on free base porphyrin as a chromoionophore

In this work, the possibility of application of free base porphyrin as a lipophilic pH chromoionophore for the preparation of optical cation-selective sensors was investigated. The properties of polymeric membranes, containing porphyrins of different structures, namely tetraphenylporphyrin (TPP) and octaethylporphyrin (OEP), were compared. Changes in equilibrium between protonated and deprotonated form of porphyrin, resulting from variations in ACh concentration, were evaluated. The influence of various factors (kind and quantity of anionic additive and porphyrin in the membrane phase, pH of sample solution) on initial equilibrium was studied. The best membrane composition was chosen as: TPP 3 wt.%, KTFPB 175 mol.% relative to ionophore, PVC:o-NPOE (1 : 4) and measuring buffer solution: 0.05 M MES, pH 4.5. Selectivity, response stability, reversibility and repeatability tests were carried out for chosen sensor. Developed sensor allowed for the determination of a model analyte, acetylcholine, at the concentration range of 10(-5) to 10(-2) M, both in stationary and flow-injection system. Sensor response was reversible and repeatable in the mentioned concentration range.