Thermochromic cellulose fibers

A method of obtaining thermochrome cellulose fibers has been developed. The basis technology used to form fibers was the Lyocell process. This method is based on spinning fibers from concentrated solvents of cellulose, using dry‐wet method in aqueous solidification bath. The cellulose solvent used in this process was N‐oxide‐N‐methylomorpholine (NMMO). The studies were to check on the features of the fibers obtained from solvents with thermochrome pigmentation, in order to evaluate their practical use. Thermochrome modifier used in the experiment was Chromicolor®AQ‐INK, Magenta type#27 pigmentation. This modifier was introduced into the spinning solutions in such amounts that fibers obtained from them would contain 1–10 wt% of pigmentation. Fibers formed out of modified solvents underwent spectral values, thermal, physicomechanical analyses, also their sorption features were evaluated. Copyright © 2007 John Wiley & Sons, Ltd.     

An accurate non-Born-Oppenheimer calculation of the first purely vibrational transition in LiH molecule

In this work we study the ground and the first vibrationally excited states of LiH molecule. We performed an extensive nonrelativistic variational calculations of the two states without using the Born-Oppenheimer approximation. The results are analyzed and compared with the data extracted from recent experiments. The 0<--1 transition energy obtained in the calculations converged to a value which is less than a wave number above the transition energy estimated from the available experimental data concerning the LiH rovibrational transitions. We discuss the remaining discrepancy and the procedure used to determine the "experimental" transition frequencies.     

Actions of compact quantum groups on -algebras

In this paper we investigate a structure of the fixed point algebra under an action of compact matrix quantum group on a -algebra . We also show that the categories of -comodules in and inner endomorphisms restricted to the fixed point algebra coincide when the relative commutant of the fixed point algebra is trivial. Next we show a version of the Tannaka duality theorem for twisted unitary groups.

     

Ion insertion into ionic liquid supported toluene generated by electrochemical redox reaction

Ion transfer across the toluene|water, toluene–ionic liquid mixture|water and ionic liquid|water boundary generated by electrochemical redox reaction of tert-butylferrocene (tBuFc) was studied with the glassy carbon (GC) electrode partially covered by the organic liquid deposit and immersed in the aqueous electrolyte solution. The electrooxidation of the redox probe in toluene deposit is followed by ejection of newly formed cation into the aqueous solution. The same reaction in the toluene–ionic liquid deposit promotes anion insertion. This pathway is also found at the electrode modified with ionic liquid.     

Introducing hydrophilic carbon nanoparticles into hydrophilic sol-gel film electrodes

A hydrophilic carbon nanoparticle–sol-gel electrode with good electrical conductivity within the sol-gel matrix is prepared. Sulfonated carbon nanoparticles with high hydrophilicity and of 10–20 nm diameter (Emperor 2000) are co-deposited onto tin-doped indium oxide substrates employing a sol-gel technique. The resulting carbon nanoparticle-sol-gel composite electrodes are characterized as a function of composition and salt (KCl) additive. Scanning electron microscopy and voltammetry in the absence and in the presence of a solution redox system suggest that the composite electrode films can be made electrically conducting and highly porous to promote electron transport and transfer. The effect of the presence of hydrophilic carbon nanoparticles is explored for the following processes: (1) double layer charging, (2) diffusion and adsorption of the electrochemically reversible solution redox system 1,1′-ferrocenedimethanol, (3) electron transfer to the electrochemically irreversible redox system hydrogen peroxide, and (4) electron transfer to the redox liquid tert-butylferrocene deposited into the porous composite electrode film. The extended electrochemically active hydrophilic surface area is beneficial in particular for surface sensitive processes (1) and (3), and it provides an extended solid|organic liquid|aqueous solution boundary for reaction (4). The carbon nanoparticle–sol-gel composite electrodes are optimized to provide good electrical conductivity and to remain stable during electrochemical investigation.     

Competing patterns of weak directional forces in pressure-frozen CH2ClI and CH2I2

Isostructural relations and phase transitions of dihalomethanes have been rationalized by the competing patterns of CH...halogen hydrogen bonds and halogen...halogen interactions, the common weak directional interactions in soft organic matter. Pressure-frozen chloroiodomethane, CH(2)ClI, at 295 K and 0.72 GPa forms centrosymmetric phase III, which at ca. 400 K and 1.6 GPa disproportionates into CH(2)Cl(2) and CH(2)I(2). The directional character of intermolecular contacts between halogen atoms results from the characteristic anisotropic charge distribution on molecular surface.     

Two-dimensional miscibility studies of alamethicin and selected film-forming molecules

Alamethicin (ALM), a 20-amino acid antibiotic peptide (peptaibol) from fungal sources, was mixed in Langmuir monolayers with six different surfactants: semifluorinated (F6H18, F10H19, F8H10OH, F6H10SH) and hydrogenated (C18SH and DODAC), aimed at finding appropriate molecules for ALM incorporation for nanodevice construction. Alamethicin-containing mixed monolayers were investigated by means of surface manometry (pi-A isotherms) and Brewster angle microscopy (BAM). Our results show that only semifluorinated alkanes can serve as an appropriate material since they form miscible and homogeneous monolayers with ALM within the whole concentration range. All the remaining surfactants, possessing polar groups, were found to demix with ALM. This effect was explained as being due to the existence of strong polar interactions between vertically oriented surfactant molecules, which tend to separate from horizontally oriented alpha-helices of the peptide. On the contrary, semifluorinated alkanes, lacking any polar group in their structure and bearing a large dipole moment, interact with ALM, also possessing a huge cumulative dipole moment. These dipole-dipole interactions between ALM and SFAs are more attractive than those between SFA molecules in their pure monolayers, causing the large ALM molecule, situated parallel to the interface, to be surrounded by SFA molecules in perpendicular orientation, leading to the formation of a highly organized binary mixed monolayer. BAM images of the ALM monolayer indicate that this peptide collapses with the nucleation and growth mechanism, like the majority of surfactants, which contradicts the model of ALM collapse by desorption, previously published in the literature.     

From nonpolar to ferroelectric crystal structure: the temperature-tuned growth of two guanidinium ethoxysulfonate polymorphs

Guanidinium ethoxysulfonate, [C(NH2)3]+[C2H5O-SO3]-, was synthesized, and two polymorphs, both stable at normal conditions, were grown from an aqueous solution by only a slight change in the crystallization temperature. The nonpolar polymorph I is built of hydrogen-bonded bilayers, while the ferroelectric polymorph II consists of single-layers. The diversity in the crystals' architecture and properties originates from the excessive number of proton-acceptor sites. At 298 K, the structure of polymorph I is orthorhombic, space group Pbam, formed of supramolecular hydrogen-bonded sheets. Within such a sheet, the ethoxysulfonate anions assume alternately cis and trans conformations, both disordered at room temperature and at 150 K. The anisotropy of the crystal structure is mirrored by a strong anisotropy of its thermal expansion. Upon cooling at 120 K, the crystal undergoes a first-order order-disorder phase transition. The structure of polymorph II is also reinforced by the two-dimensional network of NH...O hydrogen bonds, but the supramolecular motif formed is different from that of polymorph I. The H-bonded strongly corrugated sheets are stacked, forming a densely packed single-layer structure. All the anions assume the same trans conformation. At 298 K, they are disordered between the two sites related by the mirror symmetry plane. The onset of ordering of the anions coincides with the Curie point at TC = 211 K, at which the dielectric constant exceeds 4000. The continuous paraelectric-ferroelectric phase transition is associated with the symmetry change Pnma --> Pna21. Despite the apparent order-disorder character of the transition, the transition mechanism also involves a substantial displacement of the ions and a rearrangement of the H-bonded network.     

1,1-Dichloroethane: a molecular crystal structure without van der Waals contacts?

Isochoric and isobaric freezing of 1,1-dichloroethane, CH3CHCl2, mp=176.19 K, yielded the orthorhombic structure, space group Pnma, with the fully ordered molecules, in the staggered conformation, located on mirror planes. The CH3CHCl2 ambient-pressure (0.1 MPa) structures were determined at 160 and 100 K, whereas the 295 K high-pressure structures were determined at 0.59 and 1.51 GPa. At 0.1 MPa, all intermolecular distances are considerably longer than the sums of the van der Waals radii, and only a pressure of about 1.5 GPa squeezed the Cl...Cl and Cl...H contacts to distances commensurate with these sums. The exceptionally large difference between the melting points of isomeric 1,1- and 1,2-dichloroethane can be rationalized in terms of their molecular-packing efficiency. It has been shown that the location of atoms in molecules affects their intermolecular interactions, and hence their van der Waals radii are the function of molecular structures.