Inexpensive synthesis of 1,4-bis(4-aminophenoxy)-2- (6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl) phenylene and its oxygen-plasma resistant polyamides

Inexpensive synthesis of diamine, 1,4-bis(4-nitrophenoxy)-2-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl) phenylene was revealed in this work. Based on the diamine, a series of organosoluble polyamides were prepared by direct polycondensation of the diamine with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. The number-average molecular weights of the resulting polyamides range from 4.2 × 10⁴ to 10.5 × 10⁴ g/mol, and the weight-average molecular weights are in the range of 7.5-28.2 × 10⁴ g/mol. The T_gs of these polyamides range from 210 to 255 °C by dynamic mechanical analysis. The resulting polyamides are tough and flexible with tensile strength, elongation at break and moduli range from 84 to 101 MPa, 4.8-7.0%, and 2.36-3.22 GPa, respectively. The degradation temperatures (T_d 5%) and char yields at 800 °C in nitrogen range from 460 to 486 °C and 59-68 wt%, respectively. The cutoff wavelength of these polyamides falls in the range of 345-366 nm, showing a very light color characteristic. In addition, these polyamides display good oxygen plasma resistance.     

Reduction of cycle time by addition of silicon carbide filler to syndiotactic polystyrene/glass fiber composites

Reducing cycle time in injection molding process is important because it can save operational cost and increase product yield. Cycle time can be categorized by six criteria, which are metering time, time for closing a mold, packing time, holding time, cooling time, and the time needed to open a mold and to eject the molded product. It was found that the metering time is crucial to predict the cycle time of glass fiber reinforced syndiotactic polystyrene (sPS/GF, 60/40 by weight). In many cases, however, cycle time could be reduced by saving cooling time. This study is motivated by the demand to reduce the cycle time of sPS/GF composite. Since the increase of thermal conductivity leads to the reduction of cooling time, silicon carbide (SiC) is employed to evaluate if it can increase the thermal conductivity of sPS/GF composite. When SiC is added to replace entire GF in sPS/GF composite, the mechanical property of the resulting sPS/SiC (60/40 by weight) composite was not satisfied even though its thermal conductivity was enhanced to about 62 %. Within tolerable ranges in mechanical properties, SiC was added to replace a half amount of existing GF filler. sPS/GF/SiC (60/20/20 by weight) composite achieved the enhancement of thermal conductivity from 0.230 to 0.308 W/m K (34 %) which resulted in the effective reduction of both cooling time and cycle time from 16 to 10 s and from 47 to 38 s, respectively. It should be noted that additional time saving was obtained by 3 s between 6 s in cooling and 9 s in overall cycle time. It can be interpreted by the fact that the increase of thermal conductivity also accelerated the heating rate of sPS/GF/SiC composite.     

Artificial in-plane ordering of textured YBa2Cu3O7?x films deposited on polycrystalline yttria-stabilized zirconia substrates

Anisotropie surface texturing of the polycrystalline yttria-stabilized zirconia substrates, prior to YBa₂Cu₃O_7–x film deposition, is shown to promote in-plane (basal plane) ordering of the film growth in addition to thec-axis texturing. TheJ _c 's of the films in the weak-link-dominated low-field regime are enhanced considerably, and this result is attributed to the reduction of weak links resulting from a reduction in the number of in-plane large-angle grain boundaries.The authors acknowledge the support and encouragement of V. G. Keramidas and P. L. Key. This work was supported by the Electric Power Research Institute (Contract No. RP 7911-13).     

Silver(I) Polymer of Tripodal Amine: Synthesis,Structure and Photoluminescence

Starting from tripodal ligand tris-(methyl-imidazole) amine (1) the colourless complex tris-(methyl-imidazole)aminesilver(I)perchlorate (2) has been synthesized, characterized by IR, UV/Vis and ¹HNMR spectroscopic studies and finally solid state structure has been established by single crystal X-ray diffraction studies. A single crystal X-ray structure determination revealed the formation of coordination polymer. The crystal structure possesses weak d¹⁰–d¹⁰ ‘argentophilic’ interactions with Ag–Ag separation (3.348 Å). The weak luminance at 375 nm may be this Ag–Ag weak interaction. The molecule possesses weak H-bonding with C2 and C4H of imidazole with oxygen of ClO₄.     

High-efficiency, solid-state, dye-sensitized solar cells using hierarchically structured TiO₂ nanofibers

High-performance, room-temperature (RT), solid-state dye-sensitized solar cells (DSSCs) were fabricated using hierarchically structured TiO? nanofiber (HS-NF) electrodes and plastic crystal (PC)-based solid-state electrolytes. The electrospun HS-NF photoelectrodes possessed a unique morphology in which submicrometer-scale core fibers are interconnected and the nanorods are dendrited onto the fibers. This nanorod-in-nanofiber morphology yielded porosity at both the mesopore and macropore level. The macropores, steming from the interfiber space, afforded high pore volumes to facilitate the infiltration of the PC electrolytes, whereas the mesoporous nanorod dendrites offered high surface area for enhanced dye loading. The solid-state DSSCs using HS-NFs (DSSC-NF) demonstrated improved power conversion efficiency (PCE) compared to conventional TiO? nanoparticle (NP) based DSSCs (DSSC-NP). The improved performance (>2-fold) of the DSSC-NFs was due to the reduced internal series resistance (R(s)) and the enhanced charge recombination lifetime (τ(r)) determined by electrochemical impedance spectroscopy and intensity modulated photocurrent/photovoltage spectroscopy. The easy penetration of the PC electrolytes into HS-NF layers via the macropores reduces R(s) significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τ(r) difference between the DSSC-NF and DSSC-NP in the PC electrolytes was extraordinary (~14 times) compared to reported results in conventional organic liquid electrolytes. The optimized PCE of DSSC-NF using the PC electrolytes was 6.54, 7.69, and 7.93% at the light intensity of 100, 50, and 30 mW cm?2, respectively, with increased charge collection efficiency (>40%). This is the best performing RT solid-state DSSC using a PC electrolyte. Considering the fact that most reported quasi-solid state or nonvolatile electrolytes require higher iodine contents for efficient ion transport, our HS-NFs are a promising morphology for such electrolytes that have limited ion mass transport.     

A perturbation analysis on solid polymer surfaces

A linear stability model was formulated to analyze the perturbation of solid polymer surfaces. Surface energy and thermal stress were considered as the main variables. The surface tends to more unstable as the temperature increase. This is interpreted as the dominancy of the lattice vacancy diffusion over surface mass diffusion and the increase in thermal stress.     

The swirling round laminar jet

The swirling round laminar jet in an unbounded viscous fluid is investigated in this paper. The axisymmetric laminar jet with a swirling velocity is simulated by a linear-momentum source and an angular-momentum source, both located at the origin. The first-order and the second-order solutions in the far field have been obtained by solving the complete Navier—Stokes equations. It is found that the first-order solution is the well-known round-laminar-jet solution without the swirling velocity obtained by Landau [2] and Squire [3]. The second-order solution represents a pure rotating flow. The swirling velocity predicted by the present solution is compared with that obtained by Loitsyanskii [15] and Görtler [16], who solved the corresponding boundary-layer equations. It is found that the swirling velocity predicted by the present theory is smaller than that obtained from the boundary-layer equations.     

Synthesis and electrical properties of poly[2-(2-(4-trifluoromethyl)phenyl)ethenyl-1,4-phenylenevinylene] and PPV copolymers

Summary Poly[2-(2-(4-(trifluoromethyl)phenyl)ethenyl)-5-methoxy-1,4-phenylenevinylene] (PFEMPV) and a series of PPV copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and third-order nonlinear optical properties were studied. The PFEMPV films could not be doped with I₂, but FeCl₃-doped films showed an electrical conductivity of 5.0x10^-4 S/cm. The conductivities of FeCl₃-doped copolymer films ranged from 2.0x10^-3 to 2.0 S/cm depending on their copolymer compositions. The third-order nonlinear optical susceptibility, ⁽³⁾(–;,,–), was also investigated by the degenerate four wave mixing technique at 602 nm. The ⁽³⁾ value of PFEMPV was 6.9x10^-11 esu. The photoluminescence spectrum of PFEMPV shows its emission maximum at 550 nm.