Synthesis and styrene polymerization properties of dinuclear half-titanocene complexes with xylene linkage

The new dinuclear half-sandwich complexes of titanium with xylene bridge, [Ti(η⁵-cyclopentadienyl)Cl₂L]₂[CH₂-C₆H₄-CH₂] (L = Cl (3), L = O-2,6-iPr₂C₆H₃ (4), L = N(SiMe₃)(2,6-Me₂C₆H₃) (5)), have been synthesized. The complexes 4 and 5 have been prepared by the reaction of the complex 3 with the corresponding lithium salts of aryloxy and anilide. Structure of these complexes has been characterized by ¹H and ¹³C NMR. The change of substituent from chloride, 3, to anilide, 5, at titanium resulted in chemical shift change of cyclopentadienyl protons from 6.92 and 6.79 to 6.13 and 5.95 ppm probably due to the positive electron density delivery from the anilide group. It was found that all three half-titanocenes were effective catalyst for the generation of SPS (syndiotactic polystyrene). Xylene bridged dinuclear catalyst (4) with aryloxy substituent exhibited very high activity (458 kg of SPS/(mol of [Ti])h), at 40 °C, whereas the analogous hexamethylene bridged dinuclear half-titanocene catalyst (7) showed a lower activity (80.7 kg of SPS/(mol of [Ti])h) under the same conditions. While the catalyst 3 was the most active catalyst among three complexes less than 40 °C the catalyst 5 exhibited the highest activity at 70 °C. Xylene linkage was suggested to be too stiff to permit any kind of intramolecular interaction between two active centers. Lack of steric disturbance due to the rigidity of the xylene bridge might give rise to the similar properties of dinuclear metallocene to the corresponding mononuclear metallocene to result in not only the facile coordination of monomer at the active center to lead high activity but also the easier β-H elimination comparing to the dinuclear catalysts with the flexible bridge to result in the formation of lower molecular weight polymer.     

Analysis of optodynamic sources generated during laser-induced breakdown in water

We propose a method for evaluating the size of the laser-induced breakdown region in water based on the detection and analysis of optodynamic waves. The breakdown region is an optodynamic source of pressure waves that propagate into the surrounding liquid as an ultrasonic pulse. In the experiment the optical breakdown was generated by a standard ophthalmic Nd:YAG laser with a pulse duration of 10 ns and a maximum energy per pulse of 10 mJ. The pulses were detected inside the liquid with a laser-beam deflection probe. The waveforms were captured in the far-field and analyzed. The analysis provides information about the apparent size of the optodynamic source, which is directly related to the size of the breakdown region. The proposed method can be adapted for online monitoring.     

The synthesis of 12-membered macrocycles containing a C1–C8 alkene unit via ring-closing metathesis

Model cross and ring-closing metathesis strategies toward the C1–C8-linear carbon skeleton are presented. The introduction of a four-atom tether enables the formation of 12-membered rings in good-to-excellent yields and stereoselectivity. Furthermore, the study revealed that the cross-metathesis approach and the formation of medium ring sizes via ring-closing metathesis are much less favorable.     

A short synthetic route to biologically active (+/-)-daurichromenic acid as highly potent anti-HIV agent

The efficient total synthesis of biologically interesting (+/-)-daurichromenic acid is accomplished starting from 2,4-dihydroxy-6-methylbenzoic acid or 2,4-dihydroxy-6-methylbenzaldehyde in one or two steps.     

Efficient synthesis of tetrahydroquinolinones by acetic acid-mediated formal [3+3] cycloaddition

Abstract  

A simple and efficient method to synthesize a variety of tetrahydroquinolinones was successfully achieved by reacting various β-enaminones with several α,β-unsaturated aldehydes. This strategy can be viewed as a Br?nsted acid-mediated formal [3+3] cycloaddition.     

Continuous Production of Functionalized Polymer Particles Employing the Phase Separation in Polymer Blend Films

This study reports a continuous prepartion of spherical or hemispherical polymer particles simply utilizing the phase separation in polymer blend films during the coating process. We took an advantage of the strong phase separation between a water‐soluble crystalline polymer as a matrix and hydrophobic polymers as minor components. We demonstrated the prepartion of water‐soluble polystyrene (PS) particles, nitrilotriacetic acid (NTA)‐functionalized PS particles for protein separation, and semiconducting poly(3‐hexylthiophene) (P3HT) particles. The sizes of the particles could be controlled by adjusting the film thickness and weight fraction of the minor component polymers in the blend film. It provides a simple facile way to prepare polymer particles in a continous process.

     

Synthesis of 7-Hydroxyspiropyran

The 7-acetoxyspiropyrans (4a and 4b) have been prepared by the reaction of Fischer's bases (3) with 2,4-diacetoxybenzaldehyde in refluxing ethanol in moderate yields. The acetyl group of 7-acetoxy-spiropyran 4a was easily removed to give a 7-hydroxyspiropyran 6 in high yield under the basic condition.     

Synthesis of 1,3-Diketones by Reaction of α-Haloketones with Acyl Cyanides Promoted by Samarium Diiodide

α-Haloketones reacted with acyl cyanides to form 1,3-diketones in the presence of samarium diiodide. The reaction was assumed to proceed via a mechanism involving samarium enolates formed in situ from α-haloketones.     

Mechanisms Involved in the Modification of Textiles by Non-Equilibrium Plasma Treatment

Plasma methods are often employed for the desired wettability and soaking properties of polymeric textiles, but the exact mechanisms involved in plasma–textile interactions are yet to be discovered. This review presents the fundamentals of plasma penetration into textiles and illustrates mechanisms that lead to the appropriate surface finish of fibers inside the textile. The crucial relations are provided, and the different concepts of low-pressure and atmospheric-pressure discharges useful for the modification of textile’s properties are explained. The atmospheric-pressure plasma sustained in the form of numerous stochastical streamers will penetrate textiles of reasonable porosity, so the reactive species useful for the functionalization of fibers deep inside the textile will be created inside the textile. Low-pressure plasmas sustained at reasonable discharge power will not penetrate into the textile, so the depth of the modified textile is limited by the diffusion of reactive species. Since the charged particles neutralize on the textile surface, the neutral species will functionalize the fibers deep inside the textile when low-pressure plasma is chosen for the treatment of textiles.     

Development of a new contactless dielectrophoresis system for active particle manipulation using movable liquid electrodes

This study presents a new DEP manipulation technique using a movable liquid electrode, which allows manipulation of particles by actively controlling the locations of electrodes and applying on–off electric input signals. This DEP system consists of mercury as a movable liquid electrode, indium tin oxide (ITO)‐coated glass, SU‐8‐based microchannels for electrode passages, and a PDMS medium chamber. A simple squeezing method was introduced to build a thin PDMS layer at the bottom of the medium chamber to create a contactless DEP system. To determine the operating conditions, the DEP force and the friction force were analytically compared for a single cell. In addition, an appropriate frequency range for effective DEP manipulation was chosen based on an estimation of the Clausius–Mossotti factor and the effective complex permittivity of the yeast cell using the concentric shell model. With this system, we demonstrated the active manipulation of yeast cells, and measured the collection efficiency and the dielectrophoretic velocity of cells for different AC electric field strengths and applied frequencies. The experimental results showed that the maximum collection efficiency reached was approximately 90%, and the dielectrophoretic velocity increased with increasing frequency and attained the maximum value of 10.85 ± 0.95 μm/s at 100 kHz, above which it decreased.