Dyeing behaviour of lyocell fabric: effect of NaOH pre-treatment

To understand the effect of alkali pre-treatment on the dyeing of lyocell fabrics, samples are pre-treated with 0.0–7.0 mol dm⁻³ NaOH using a pad-batch process and then dyed with different types of reactive dyes. Exhaustion, fixation, and visual colour strength (K/S values) are measured. It is observed that sodium hydroxide pre-treatment significantly improves the colour yield, exhaustion, and fixation for all dyes used. Highest K/S values are obtained when the fabrics are pre-treated with 2.0–2.5 mol dm⁻³ NaOH. Cross-sectional analysis shows that below this optimum concentration the core fibres in the yarn are not dyed; at optimum concentration all fibres in yarn cross-section are homogeneously dyed. Cross-sectional analysis shows that as the pre-treatment concentration of NaOH increases above 2.5 mol dm⁻³, the fibres change progressively from a circular to angular cross-section, forming a solid unit. The decrease in K/S above the treatment concentration of 2.5 mol dm⁻³, though the %E and %F remains almost constant, is attributed to the distribution of dye over a larger surface area of the outer fibres in the yarn cross section, forcing the K/S at λ_max to decrease. This paper was presented at the 2nd International Cellulose Conference, Tokyo, Japan, 24th October 2007.     

22pi smaragdyrin molecular conjugates with aromatic phenylacetylenes and ferrocenes: Syntheses, electrochemical, and photonic properties

Syntheses, spectroscopic, electrochemical, and third-order nonlinear optical susceptibilities of a series of 22pi smaragdyrins and their corresponding Rh(I) derivatives bearing phenylacetylene substituents and ferrocene-containing substituents are reported. The synthetic strategy involved a [3 + 2] acid-catalyzed oxidative coupling reaction of the appropriate dipyrromethane and oxatripyrrane. The desired meso substituents, such as phenylacetylenylphenyl and the ferrocenes, were incorporated to the dipyrromethane unit prior to the oxidative coupling reaction. The optical absorption, emission characteristics, and the quantum yield of the smaragdyrin conjugates depends on the nature of the substituent, nature of linker group, and the spacer length. Theoretical studies at the DFT level suggest high delocalization of electrons confined to only four of the five available heterocyclic rings for the free bases. However, upon Rh(I) metalation, the pi-electron delocalization is extended to all the heterocyclic rings. The two-photon absorption cross section (TPA) values sigma(2) measured through the open aperture Z-scan method, increases linearly with enhanced pi-electron delocalization for the smaragdyrins containing phenylacetylene substituents. The meta branching of substituents decreases sigma(2) values. Introduction of Rh(I) to the smaragdyrin cavity enhances the sigma(2) values by about 3-10 orders of magnitude, attributed to the increased aromatic character upon Rh(I) insertion. The calculated molecular electrostatic potential (MESP) and harmonic oscillator model of aromaticity (HOMA) for the free bases and the Rh(I) derivatives justifies such a conclusion. A linear correlation observed for the second oxidation potential of Rh(I) derivatives and corresponding free bases also support the increased aromaticity upon Rh(I) insertion. The electrochemical data for ferrocene-containing smaragdyrins reveal easier ring oxidation by about 50-130 mV and harder ferrocene oxidation by 40-180 mV suggesting electron-donating nature of the ferrocene upon linking with the smaragdyrin system. The TPA cross section value of 88782 GM observed for 5g represents one of the highest values known for a metalloexpanded porphyrin derivative.     

Independent isomeric yield ratios of 95m,gNb in the natMo(γ, pxn) and natZr(p,xn) reactions

The independent isomeric yield ratios of ^95m,gNb from the ^natMo(γ, pxn) reactions with bremsstrahlung end-point energies of 45, 50, 55, 60, and 70 MeV were determined by an activation and an off-line γ-ray spectrometric technique at the Pohang accelerator laboratory (PAL), Korea. The isomeric yield ratios of ^95m,gNb from the ^natZr(p, xn) reactions were also determined in eight different proton energies within 19.4–44.7 MeV by a stacked-foil activation and an off-line γ-ray spectrometric technique using the MC-50 cyclotron of Korea Institute of Radiological and Medical Sciences (KIRAMS), Korea. The measured isomeric yield ratios of ^95m,gNb from the present work and the literature data in the ^natMo(γ, pxn) and ^natZr(p, xn) reactions were compared with the similar literature data in the ^natMo(p, αxn) reactions. It was found that the isomeric yield ratio of ^95m,gNb increases with projectile energy, which indicate the effect of excitation energy. However, at the same excitation energy, the isomeric yield ratios of ^95m,gNb in the ^natZr(p, xn) and ^natMo(p, αxn) reactions are higher than those in the ^natMo(γ, pxn) reaction, which indicates the role of input angular momentum. The isomeric yield ratios of ^95m,gNb in the ^natMo(γ, pxn), ^natZr(p, xn), and ^natMo(p, αxn) reactions were also calculated using computer code TALYS 1.4. The calculated isomeric yield ratios of ^95m,gNb from three reactions increase with excitation energy. However, in all the three reactions, the calculated values are significantly higher than the experimental data.     

TDCR measurements of 3H, 63Ni and 55Fe using Hidex 300SL LSC device

The commercial Hidex LSC system has been used to measure triple to double coincidence ratio (TDCR), experimental counting efficiency (CE) and the absolute activity for radioactive standards of pure beta emitters viz. ³H, ⁶³Ni and ⁵⁵Fe, an electron capture nuclide. Colour and chemical quench measurements of ⁶³Ni and ⁵⁵Fe have been done. An excellent match between TDCR and CE has been obtained for beta emitters, while very large deviations have been observed for ⁵⁵Fe. The deviation between TDCR and experimental efficiency has been found to be nearly uniform. Based on this, an empirical correction factor for TDCR which gives the correct efficiency has been evaluated, to enable efficient application of this commercial instrument for ⁵⁵Fe estimation. These TDCR correction factors were further validated by applying for ⁵⁵Fe activity measurements in ASTM standard steel samples irradiated to a fixed neutron flux in research reactor CIRUS. Finally, ⁵⁵Fe activity in steel sample from APSARA reactor decommissioning waste was successfully estimated using this modified TDCR.     

A Triphenyl Amine‐Based Solvatofluorochromic Dye for the Selective and Ratiometric Sensing of OCl− in Human Blood Cells

A new visible‐light‐excitable fluorescence ratiometric probe for OCl^? has been developed based on a triphenylamine‐diamiomaleonitrile (TAM) moiety. The structure of the dye was confirmed by single‐crystal X‐ray analysis. It behaves as a highly selective and sensitive probe for OCl^? over other analytes with a fast response time (～100 s). OCl^? reacts with the probe leading to the formation of the corresponding aldehyde in a mixed‐aqueous system. The detection limit of the probe is in the 10^?8 M range. The probe (TAM) also exhibits solvatofluorochromism. Changing the solvent from non‐polar to polar, the emission band of TAM largely red‐shifted. Moreover, the probe shows an excellent performance in real‐life application in detecting OCl^? in human blood cells. The experimentally observed changes in the structure and electronic properties of the probe after reaction with OCl^? were studied by DFT and TDDFT computational calculations.     

A crossed molecular beams and ab initio study on the formation of C6H3 radicals. an interface between resonantly stabilized and aromatic radicals

The crossed molecular beams reaction of dicarbon molecules, C(2)(X(1)Σ(g)(+)/a(3)Π(u)) with vinylacetylene was studied under single collision conditions at a collision energy of 31.0 kJ mol(-1) and combined with electronic structure calculations on the singlet and triplet C(6)H(4) potential energy surfaces. The investigations indicate that both reactions on the triplet and singlet surfaces are dictated by a barrierless addition of the dicarbon unit to the vinylacetylene molecule and hence indirect scattering dynamics via long-lived C(6)H(4) complexes. On the singlet surface, ethynylbutatriene and vinyldiacetylene were found to decompose via atomic hydrogen loss involving loose exit transition states to form exclusively the resonantly stabilized 1-hexene-3,4-diynyl-2 radical (C(6)H(3); H(2)CCCCCCH; C(2v)). On the triplet surface, ethynylbutatriene emitted a hydrogen atom through a tight exit transition state located about 20 kJ mol(-1) above the separated stabilized 1-hexene-3,4-diynyl-2 radical plus atomic hydrogen product; to a minor amount (<5%) theory predicts that the aromatic 1,2,3-tridehydrobenzene molecule is formed. Compared to previous crossed beams and theoretical investigations on the formation of aromatic C(6)H(x) (x = 6, 5, 4) molecules benzene, phenyl, and o-benzyne, the decreasing energy difference from benzene via phenyl and o-benzyne between the aromatic and acyclic reaction products, i.e., 253, 218, and 58 kJ mol(-1), is narrowed down to only ～7 kJ mol(-1) for the C(6)H(3) system (aromatic 1,2,3-tridehydrobenzene versus the resonantly stabilized free radical 1-hexene-3,4-diynyl-2). Therefore, the C(6)H(3) system can be seen as a "transition" stage among the C(6)H(x) (x = 6-1) systems, in which the energy gap between the aromatic isomer (x = 6, 5, 4) is reduced compared to the acyclic isomer as the carbon-to-hydrogen ratio increases and the acyclic isomer becomes more stable (x = 1, 2).     

Structure and dynamics of poly(oxyethylene) cholesteryl ether wormlike micelles: rheometry, SAXS, and cryo-TEM studies

In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO(20)) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The ChEO(20) self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η(0)) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η(0?max)) increased with the increasing ChEO(20) mixing fraction with water. We observed that η(0?max) increased by 2 to 4 orders of magnitude as a function of the ChEO(20) concentration. The Maxwell relaxation time (τ(R)) shows a maximum value at a concentration corresponding to η(0?max) (i.e., τ(R) increases with L-02 concentration and then decreases after attaining a maximum value, whereas the plateau modulus (G(0)) shows monotonous growth). These observations demonstrate microstructural transitions in two different modes: L-02 first induces 1-D micellar growth and as a result the viscosity increases, and finally after the system attains its maximum viscosity, L-02 causes branching in the network structures. The microstructure transitions are confirmed by SAXS and cryo-TEM techniques.     

Dielectric and electro-optic properties of two biphenylyl benzoate-based ferroelectric mesogens with tilted hexagonal phases

ABSTRACT

Two partially fluorinated ferroelectric liquid crystals (2F3R, 3F3R) with biphenylyl benzoate core have been investigated by frequency domain dielectric spectroscopy and electro-optic method. Both the compounds exhibit SmC* phase over a wide range of temperature along with tilted hexatic phase SmF* and soft crystal phases SmJ* (in 2F3R) and SmG* (in 3F3R) and one coexistence phase of (SmF*+SmC*). Both BOO phason and tilt phason relaxations are observed in SmF* phase and cooperative relaxation behaviour is also observed in crystal-like smectic phases. Goldstone mode relaxation is observed in SmC* phase and Maxwell Wagner mode is observed in all the phases. In 2F3R soft mode is detected in both SmC* and SmA* phases but not in 3F3R which melts directly to isotropic phase from SmC* phase. Compounds possess moderate values of spontaneous polarisation and exhibit quite sharp electrical response especially in 2F3R. Rotational viscosities, pitch and elastic constant are also measured. Effect of chain length and fluorination on various physical parameters has been discussed.     

Regioselective Insertion of Aluminum(I) in the cyclo‐P5 Ring of Pentaphosphaferrocene

A route to directly access mixed Al–Fe polyphosphide complexes was developed. The reactivity of pentaphosphaferrocene, [Cp*Fe(η⁵‐P₅)] (Cp*=C₅Me₅), with two different low‐valent aluminum compounds was investigated. The steric and electronic environment around the [Al^I] centre are found to be crucial for the formation of the resulting Al–Fe polyphosphides. Reaction with the sterically demanding [Dipp‐BDIAl^I] (Dipp‐BDI={[2,6‐ⁱPr₂C₆H₃NCMe]₂CH}^?) resulted in the first Al‐based neutral triple‐decker type polyphosphide complex. For [(Cp*Al^I)₄], an unprecedented regioselective insertion of three [Cp*Al^III]²⁺ moieties into two adjacent P?P bonds of the cyclo‐P₅ ring of [Cp*Fe(η⁵‐P₅)] was observed. The regioselectivity of the insertion reaction could be rationalized by isolating an analogue of the reaction intermediate stabilized by a strong σ‐donor carbene.