The first liquid crystalline phthalocyanine derivative capable of edge-on alignment for solution processed organic thin-film transistors

Tetraoctyl-substituted vanadyl phthalocyanine (OVPc4C8) as a new NIR-absorbing discotic liquid crystalline material can form highly ordered thin films with edge-on alignment of the molecules and molecular packing mode identical to that in the phase II of OVPc for solution processed OTFTs with mobility up to 0.017 cm(2) V-1 s(-1).

Controlled synthesis of nanoporous Au microsheet via surfactant emulsion template

A facile and wet-chemical approach was employed to control synthesis of self-organizing, hyperbranched nanoporous Au microsheet with high quality in bulk quantity. This method produced nanoporous Au microsheets with a thickness of 7-15 nm. The microsheets were composed of irregularly interconnected planar Au nanoplates with interstices, i.e. nanopores of 10-50 nm. And the nanoporous Au microsheets were enveloped in 10-30 nm thick polyaniline (PANI) sheaths. The morphology of the nanostructured Au composites could also be easily tuned by changing the concentration of aniline and chlorauric acid. The dendritic and epitaxial growth of nanoporous Au microsheet was believed as the diffusion-limited process confined in the lamellar emulsion phase through self-assembly of aniline and dodecylsulfate. The solution reaction proceeded at a mild condition (room temperature and aqueous solutions), and less toxic reagents were employed instead of extreme toxic and corrosive chemicals.

Nucleobase-metal hybrid materials: Preparation of submicrometer-scale, spherical colloidal particles of adenine-gold(III) via a supramolecular hierarchical self-assembly approach

We report a simple and effective supramolecular route for facile synthesis of submicrometer-scale, hierarchically self-assembled spherical colloidal particles of adenine - gold(III) hybrid materials at room temperature. Simple mixture of the precursor aqueous solutions of adenine and HAuCl4 at room temperature could result in spontaneous formation of the hybrid colloidal particles. Optimization of the experimental conditions could yield uniform-sized, self-assembled products at 1:4 molar ration of adenine to HAuCl4. Transmission electron microscopy results reveal the formation of hierarchical self-assembled structure of the as-prepared colloidal particles. Concentration dependence, ratio dependence, time dependence, and kinetic measurements have been investigated. Moreover, spectroscopic evidence [i.e., Fourier transform infrared (FTIR) and UV-vis spectra and wide-angle X-ray scattering data] of the interaction motives causing the formation of the colloidal particles is also presented.

Stabilization of metastable phase II of isotactic polybutene-1 by coated carbon

Stabilization effect on metastable phase II of isotactic polybutene-1 (iPB-1) by coated carbon has been investigated by transmission electron microscopy (TEM) and electron diffraction (ED) techniques. The results indicate that after evaporating carbon, the phase II-I crystal transformation time is greatly prolonged from 9 days for carbon-uncoated samples to 120 days for carbon-coated ones under atmospheric pressure, while under high pressure (50 bar), the phase transformation time increases from 5 min for the former to 20 min for the latter. The stabilization effect on metastable phase II of carbon coated iPB-1 is attributed to a surface fixing effect of the evaporated carbon.

An approach for synthesizing nanometer- to micrometer-sized silver nanoplates

Silver nanoplates with controlled size are synthesized by seed-mediated growth approach in the presence of citrate. These nanoplates are single crystal with a mean size of 25-1073 nm and thickness of ca. 10-22 nm. The optical in-plane dipole plasmon resonance bands of these plates can be tuned from 458 to 2400 nm. Control experiments have been explored for a more thorough understanding of the growth mechanism. It was found that the additional citrate ions in the growth solution were the key to controlling the aspect ratio of silver nanoplates. Similar to the surfactants or polymers in the solution, citrate ions could be likewise dynamically adsorbed on the growing silver nanoparticles and promote the two-dimensional growth of silver nanoparticles under certain conditions. Small silver seeds were also found to play an important role in the formation of large thin silver nanoplates, although the structure of them was not clear yet and needed further investigations.

Nucleation and growth of glycine crystals with controllable sizes and polymorphs on Langmuir-Blodgett films

Control of crystal polymorph and size is very important in many application fields. Herein we demonstrate that Langmuir-Blodgett (LB) films of stearic acid (SA) and octadecylamine (ODA) can serve as templates and generate different polymorphs of glycine crystals. In the neutral aqueous solutions, gamma-glycine crystallizes on LB films of ODA while the polymorphic outcome becomes the (x-form on LB films of SA. These observed results could be explained by the electrostatic interactions and geometric lattice matching at the LB film/crystal interfaces, respectively. By keeping the appropriate supersaturation, we have successfully controlled the number of crystals grown on LB films; for example, in some certain cases, only one piece of crystal was grown on LB films in solution. Therefore, large crystals of centimeter size could be prepared. These experimental results suggest a new approach to produce an organic crystal with bulk scale.

Transformation from ordered islands to holes in phase-separating P2VP/PS blend films by adding triton X-100

Our previous investigation showed that the ordered hexagonal island pattern in the phase-separating polymeric blend films of polystyrene and poly(2-vinylpyridine) (PS/P2VP) formed due to the convection effect by proper control of PS molecular weight, solvent evaporation rate, and the weight ratio of PS to P2VP. In this paper, we further illustrate that, by adding a proper amount of the surfactant Triton X-100 to the PS/P2VP toluene solution, the ordered hexagonal island pattern can be transformed to the ordered honeycomb pattern. The effects of the amount of Triton X-100 on the surface morphology evolution and the pattern transformation are discussed in terms of the collapse of Triton X-100, phase separation between Triton X-100/P2VP and PS, the interfacial interaction between Triton X-100/P2VP and the mica substrate, and the Benard-Marangoni convection.

Phase separation of PS/PVME blend films induced by capillary force

The phase behavior of a miscible PS/PVME (80/20, w/w) blend film in a confined geometry has been investigated at the annealing temperature much lower than the low critical solution temperature (LCST) of the blend. When the annealing temperature (52degreesC) is near the glass transition temperature of the blend (51.2degreesC), PVME-rich phase at the air-film surface under a microchannel forms smaller protrusion. When the annealing temperature is increased to 70degreesC, the protruding stripes, which are almost developed, are mainly composed of the mobile PVME-rich phase. These results reveal that the capillary force lead to the enrichment of PVME-rich phase at the air-polymer interface of a PDMS microchannel, that is, the capillary force lithography (CFL) can induce the phase separation of PS/PVME blend films.

Effects of casting solvents on the formation of inverted phase in block copolymer thin films

Previously, an inverted phase (the minority blocks comprising the continuum phase) was found in solution-cast block copolymer thin films. In this study, the effect of casting solvents on the formation of inverted phase has been studied. Two block copolymers, poly(styrene-b-butadiene) (SB) (M-w = 73 930 Da) and poly(styrene-b-butadiene-b-styrene) (SBS) (M-w = 140 000 Da), with comparable block lengths and equal polystyrene (PS) weight fraction (similar to30 wt %) were used. The copolymer thin films were cast from different solvents, toluene, benzene, cyclohexane, and binary mixtures of benzene and cyclohexane. Toluene and benzene are good solvents for both PS and PB, but have a preferential affinity for PS, while cyclohexane is a good solvent for PB but a Theta solvent for PS (T-Theta = 34.5 degreesC). The differential solvent affinity for PS and PB was estimated in terms of a difference between the polymer-solvent interaction parameter, chi, for each block. Under an extremely slow solvent evaporation rate, the time-dependent phase behavior during such a solution-to-film process was examined by freeze-drying the samples at different stages, corresponding to different copolymer concentrations, rho.

Patterned self-adaptive polymer brushes by "grafting to" approach and microcontact printing

Patterned self-adaptive PS/P2VP mixed polymer brushes were prepared by "grafting to" approach combining with microcontact printing (muCP). The properties of the patterned surface were investigated by lateral force microscopy (LFM), XPS and water condensation figures. In the domains with grafted P2VP, the PS/P2VP mixed brushes demonstrated reversible switching behavior upon exposure to selective solvents for different components. The chemical composition of the top layer as well as the surface wettability can be well tuned due to the perpendicular phase segregation in the mixed brushes. While in the domains without grafted P2VP, the grafted PS did not have the capability of switching. The development and erasing of the pattern is reversible under different solvent treatment.

Micellization and reversible pH-sensitive phase transfer of the hyperbranched multiarm PEI-PBLG copolymer

A novel, hyperbranched, amphiphilic multiarm biodegradable polyethylenimine-poly(gamma-benZyl-L-gluta- mate) (PEI-PBLG) copolymer was prepared by the ring-opening polymerization of gamma-benzyl-L-glutamate-N-car-boxyanhydride (BLG-NCA) with hyperbranched PEI as a macroinitiator. The copolymer could self-assemble into core-shell micelles in aqueous solution with highly hydrophobic micelle cores. As the PBLG content was increased, the size of the micelles increased and the critical micelle concentration (CMC) decreased. The surface of the micelles had a positive potential. The cationic micelles were capable of complexing with plasmid DNA (pDNA), which could be released subsequently by treatment with polyanions. The PEI-PBLG copolymer formed unimolecular micelles in chloroform solution. ne pH-sensitive phase-transfer behavior exhibited two critical pH points for triggering the encapsulation and release of guest molecules. Both the encapsulation and release processes were rapid and reversible. Under strong acidic or alkaline conditions, the release process became partially or completely irreversible.

Investigation of sol-gel transition in Pluronic F127/D2O solutions using a combination of small-angle neutron scattering and Monte Carlo simulation

Physical gelation in the concentrated Pluronic F127/D2O solution has been studied by a combination of small-angle neutron scattering (SANS) and Monte Carlo simulation. A 15% F127/D2O solution exhibits a sol-gel transition at low temperature and a gel-sol transition at the higher temperature, as evidenced by SANS and Monte Carlo simulation studies. Our SANS and simulation results also suggest that the sol-gel transition is dominated by the formation of a percolated polymer network, while the gel-sol transition is determined by the loss of bound solvent. Furthermore, different diffusion behaviors of different bound solvents and free solvent are observed. We expect that this approach can be further extended to study phase behaviors of other systems with similar sol-gel phase diagrams.

Synthesis of novel maleimide-terminated thioetherimide oligomer and its bulk copolymerization with reactive solvents

This paper reports the synthesis of a novel maleimide-terminated thioetherimide oligomer and its copolymefization with reactive solvents bearing vinyl. Starting from 3-chlorophthalic anhydride and 4-chlorophthalic anhydride, 2,2',3,3'-thiodiphenyl tertracaboxylic dianhydride (3,3'-TDPA) and 3,3',4,4'-thiodiphenyl tertracaboxylic dianhydride (4,4'-TDPA) were synthesized. Thereby, a novel maleimide-terminated thioetherimide oligomer was prepared from. 3,3-TDPA, 4,4'-TDPA, 3,3'-dimethyl-4,4-diaminodiphenylmethane (DMMDA) and maleic anhydride. Binary and ternary copolymer resin were derived from corresponding binary and ternary homogeous solution consisting of thioetherimide oligomer, reactive solvent N-vinylpyrrolidone (NVP) or N,N'-dimethylacrylamide (DMAA) and divinylbenzene (DVB) as modifier, initiated either by gamma ray irradiation or by benzoyl peroxide (BPO). Thermal and mechanical properties of copolymer resin are determined and compared in terms of the kind of reactive solvent, addition of modifier DVB. The effect of initiation approach on property of final copolymer resin were studied. Phase separation and sub-transition of ternary copolymer resin induced by BPO are observed, which could be accounted for by thermal movement of DMAA molecules during thermal initiation.

Preparation and characterization of a novel solid solution of aluminum in tungsten carbide by mechanically activated high-temperature reaction

In this work, a novel substitutional solid solution (W0.8Al0.2)C was synthesized by mechanically activated high-temperature reaction. X-ray diffraction was used for phase identification during the whole reaction process. Environment scanning electronic microscopy-field emission gun and energy dispersive x-ray were used to investigate the microstructure and the quantitative material composition of the specimen. (W(0.8)A(10.2))C was found to crystallize in the WC-type, and the cell parameters were a = 2.907(1) angstrom and c = 2.837(1) angstrom. The hardness of (W0.8Al0.2)C was tested to be 19.3 +/- 1 GPa, and the density was 13.19 +/- 0.05 g cm(-3).