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An ice/salt-assisted strategy has been developed to achieve the green and efficient synthesis of ultrathin two-dimensional (2D) micro/mesoporous carbon nanosheets (CNS) with the dominant active moieties of Fe-N4 (Fe-N-CNS) as high-performance electrocatalysts for the oxygen reduction reaction (ORR). The strategy involves freeze-drying a mixture of iron porphyrin and KCl salt using ice as template followed by a confined pyrolysis with KCl as an independent sealed nanoreactor to facilitate the formation of 2D carbon nanosheets, N incorporation, and porosity creation. The well-defined assembly of ultrathin 2D carbon nanosheets ensures high utilization of D1 and D3 Fe-N4 active sites, and effectively promotes the mass transport of ORR reactants by virtue of the pronounced mesoporous structure. The resulting Fe-N-CNS electrocatalyst was shown to exhibit superior ORR activity, better electrochemical durability, and methanol tolerance towards ORR in alkaline electrolyte relative to the commercial Pt/C electrocatalyst.

A fluid material with high protein content (120–310 mg mL−1) was formed through the ordered self-assembly of native proteins segregated from water. This material is instantly prepared by the simple mixing of a protein solution with anionic and cationic surfactants. By changing the ratio of the surfactants based on the electrostatic characteristics of the target protein, we observed that the surfactants could function as a versatile molecular glue for protein assembly. Moreover, these protein assemblies could be disassembled back into an aqueous solution depending on the salt conditions. Owing to the water-retaining properties of the hydrophilic part of surfactants, the proteins in this material are in a water-rich environment, which maintains their native structure and function. The inclusion of water also provides functional extensibility to this material, as demonstrated by the preparation of an enzymatically active gel. We anticipate that the unique features of this material will permit the use of proteins not only in solution but also as elements of integrated functionalized materials.

Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices.

This paper describes the reversible control of the size of liquid-metal nanoparticles under ultrasonication. Gallium was utilized as a liquid metal, which has a melting point of 29.8 °C. Investigating the effects of ultrasonication (power, time, and temperature) on the formation of gallium nanoparticles revealed that the process is similar to the formation of oil in water (O/W) or water in oil (W/O) emulsions, as the temperature significantly affects the size of the gallium nanoparticles (GaNPs). Under ultrasonication, the balance between the break-up and coalescence of the GaNPs can be adjusted by changing the temperature or adding acid through modulating the natural surface oxide layer (which can be removed with acid) and the stabilizing effect of the surfactant dodecanethiol. Coalescence was predominant at higher temperatures, whereas particle break-up was found to be predominant at lower temperatures. Furthermore, the change in size was accompanied by a shift in the plasmonic absorption of the GaNPs in the UV region.

Hybrid materials composed of phase-separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block-copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one-dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light-emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains.

The Lewis base-promoted alkynylation of fluorobenzenes using trimethylsilylacetylenes studying the reactivity as a function of the number of fluoride groups is described. The reaction of 1-(pentafluorophenyl)- and 1-(3,4,5-trifluorophenyl)-2-phenylacetylenes and 1-(4-methoxyphenyl)-2-trimethylsilylacetylene with CsF/18-crown-6 in DMSO gave the alkynylated products in moderate to good yields with high regioselectivity under mild conditions. However, the 3,4-difluorophenyl derivative showed low reactivity.

Silver microcoil is fabricated through a biotemplating process combined with electroless plating. Spiral vessels in Lotus root are employed as a biotemplate because of their left-handed coil structure. The silver microcoil exhibits a solenoidal microcoil showing self-inductance in the level of picohenry, which could be applied for electromagnetic-responsive materials in the high-frequency region such as millimeter waves or terahertz waves.

Novel wormlike nanostructures were self-assembled in bulk films of a well defined diblock copolymer with azobenzene moieties, which was prepared by atom transfer radical polymerization (ATRP). For comparison, a homopolymer with almost the same repeat units of azobenzene as those in the copolymer was also prepared. They both had well defined structures and exhibited a smectic liquid crystalline phase. Upon annealing the copolymer films, poly (methyl methacrylate) formed a matrix with excellent optical properties, and the azobenzene segment in the minority phase self-assembled into a wormlike mesogenic domain in the bulk films. Such block copolymer films exhibited stability and transparency by eliminating the scattering of visible light, indicating their potential application as photoresponsive functional materials. Although wormlike morphologies have been obtained in micelles from block copolymer solutions, to the best of our knowledge, such wormlike nanostructures have never been explored in bulk films.

In PEOm-b-PMA(Az)n amphiphilic diblock copolymers, nanoscale struc- tures exhibit an hexagonal-packed PEOm cylinders arrangement. To precisely investi- gate the role of interfacial interactions between hydrophilic PEOm and hydrophobic PMA(Az)n including mesogene sequences in the side chains, at the isotropic transi- tion, polymer systems are submitted to thermal and barometric effects under hydro- static pressure. The thermodynamic investigation is based on the original coupled calorimetric-PVT technique, yielding scanning transitiometry. Three phase diagrams can be represented versus pressure: (1) isotropic temperature described by Clapeyron equation (Tiso vs. P), (2) change of volume of the system (DViso vs. P), (3) entropy of the system (DSiso vs. P). In presence of mercury as pressure transmitting fluid, (dTiso/dP) as well as DViso and DSiso are larger for a PMA(Az)n homopolymer com- pared to those for the investigated copolymer. Additional calculations of DSiso using thermal and mechanical effects give consistent results. V C 2007 Wiley Periodicals, Inc. J

The hierarchical self-assembly behaviors of a series of amphiphilic liquid crystalline block copolymers (pEG m Az n ), consisting of poly(ethylene glycol) (pEG) block and liquid crystalline polymer block (pAz) of poly(11-[4-(4-butylphenylazo) phenoxy]-undecyl methacrylate) containing an azobenzenzene mesogen, in the selective solvent diethyleneglycol, which is good for pEG block, were studied by polarized and depolarized light scattering. It was found that these copolymers can form micellar particles with internal ordered structures of optical anisotropy. Depending on the relative lengths of the blocks, the obtained micellar structures show optical anisotropies with different geometrical anisotropies. The higher composition of pAz-core blocks leads to the larger aggregate. The lower-molecular-weight copolymers tend to form the long and thin strings, which show rather the larger size with larger aggregation number. Even at the similar composition of pAz-core block, copolymers with different chain lengths can form the core of the different aggregating structures with the different molecular orientations. It was also found that the addition of a small amount of the surfactant, C 12 E 25 , makes the string-like aggregate shorter.

A series of novel dendronized pi-conjugated poly(isocyanide)s were synthesized successfully by using a Pd-Pt mu-ethynediyl dinuclear complex ([ClPt{P(C2H5)3}2C[triple bond]CPt{P(C2H5)3}2Cl]) as the initiator. The polymerizations of the dendronized monomers follow first-order kinetics, indicating that living polymerization takes place. The obtained polymers exhibit narrow polydispersities in the range of 1.03-1.20. Thermal properties of the poly(isocyanide)s as well as their isocyanide monomers and precursors with formamido (HCONH-) moieties as apexes were investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). Both the peripheries and the apex groups of the dendrons affect the formation of supramolecular column and/or cubic phases of the precursors and monomers. The formamido precursor forms a liquid-crystalline phase due to intermolecular hydrogen bonding. The isocyanide monomer lacks this hydrogen-bonding ability and does not display an organized mesophase. All of the rigid poly(isocyanide)s with the monodendrons exhibit columnar liquid-crystalline phases. Interestingly, cylindrical structures of a poly(isocyanide) were directly visualized by using transmission electron microscopy (TEM).

A new class of liquid-crystalline (LC) homopolymers of poly{11-[4-(3-ethoxycarbonyl-coumarin-7-oxy)-carbonylphenyloxy]-undecyl methacrylate} containing a coumarin moiety as a photocrosslinkable unit with various polymerization degrees and their LC-coil diblock and LC-coil-LC triblock copolymers with polystyrene as the coil segment was synthesized with the atom transfer radical polymerization method. All the homopolymers and block copolymers synthesized here exhibited narrow polydispersities, indicating well-controlled living polymerization. Differential scanning calorimetry, polarized optical microscopy, and wide-angle X-ray diffraction confirmed that all the homopolymers and block copolymers exhibit a monolayer smectic A phase. Coumarin moieties in the polymers can be photodimerized under λ > 300 nm light irradiation to yield crosslinked network structures, which improve the thermal stability of a polymer nanostructure because of microphase separation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2197–2206, 2003

A series of novel polyisocyanide-grft-polystyrenes and polyisocyanide-graft-[polystyrene-block-poly(butyl acrylate)]s were synthesized through the grafting-through and grafting-from routes with two types of living polymerization techniques: polymerization with the Pd-Pt p-ethynediyl dinuclear complex as the initiator and catalyst for the polyisocyanide backbone and atom transfer radical polymerization for the grafted side chain. Through the introduction of a chiral center at the side chain of the polyisocyanide backbone, helical grafted and graft block polyisocyanides were prepared through the grafting-from method. All of the obtained polymers exhibited polydispersities in the range of 1.07-1.41. This might have been the first time grafted polyisocyanides were prepared, especially helical grafted polyisocyanides, through the operation of two living polymerization techniques.

Screw-sense-selective polymerization of the chiral isocyanide monomers derived from phenylalanine with NiCl2 as a catalyst in methanol to yield helical-conjugated polyisocyanide was investigated with respect to the thermal stability of its helical conformation. Poly(1-tert-butoxycarbonyl-2-phenylethyl isocyanide) (poly1c) took a stable helical conformer independent of the polymerization temperature. In poly(1-ethoxycarbonyl-2-phenylethyl isocyanide) (poly2c), which had slightly smaller side groups, the helical conformation was thermally destabilized. The specific rotation and circular dichroism of poly2c prepared at temperatures greater than 40 °C were considerably depressed in comparison with the values for poly2c prepared at or below room temperature. Additionally, poly2c prepared at low temperatures exhibited reversible temperature-dependent specific rotation and circular dichroism, whereas poly1c showed few changes. It is suggested that polyisocyanide derived from phenylalanine takes various helical conformers (i.e., from tightly to loosely coiled helices), the thermal stability of which depends on the size of the side group. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 399–408, 2002

Detailed investigations on the self-assembly of amphiphilic star block copolymers composed of three-arm poly(ethylene oxide) (PEO) and poly(methacrylate) (PMAAz) with an azobenzene side chain (denoted as 3PEO-b-PMAAz) into stable spherical aggregates with clear lamellar stripes in solution are demonstrated. Four block copolymers, 3PEO12-b-PMA(Az)33, 3PEO22-b-PMA(Az)31, 3PEO22-b-PMA(Az)62, and linear PEO68-b-PMA(Az)31, are synthesized. The liquid crystalline properties of the block copolymers are studied by differential scanning calorimetry, polarized optical microscopy techniques, and wide-angle X-ray diffraction. The morphologies of the compound micelles self-assembled in tetrahydrofuran (THF)/water mixtures are observed by means of transmission electron microscopy and scanning electron microscopy. The size of the spherical micelles is influenced by the self-assembly conditions and the lengths of two blocks. The well-defined three-arm architecture of the hydrophilic blocks is a key structural element to the formation of stable spherical compound micelles. The micelle surface integrity is affected by the lengths of PEO blocks. The lamellar stripes are clearly observed on these micelles. This work provides a promising strategy to prepare functional stable spherical compound micelles self-assembled by amphiphilic block copolymers in solution.

Nanoporous thin films with pore size of sub-10 nm are fabricated using an acid-cleavable block copolymer (BCP), a benzoic imine junction between poly(ethylene oxide) (PEO) and poly(methacrylate) (PMAAz) bearing an azobenzene side chain (denoted as PEO-bei-PMAAz) as the precursor. After a thermal annealing, the block copolymers are self-assembled to form highly ordered PEO cylinders within a PMAAz matrix normal to the film, even in the case of low BCP molecular weight due to the existing of the liquid crystalline (LC) azobenzene rigid segment. Thus, PMAAz thin films with pore size of ≈7 nm and density of ≈1012 cm−2 are obtained after removal of the PEO minor phase by breaking the benzoic imine junction under mild acidic conditions. This work enriches the nanoporous polymer films from BCP precursors and introduces the LC property as a functionality which can further enhance the mechanical properties of the films and broaden their applications.

Applications of conjugated polymers to advanced materials are demonstrated with fabrications of functional molecular materials and devices by incorporation of functional molecules to conjugated and/or conducting polymer, ultrahigh anisotropic conducting polymer materials by topological polymerizations of LB multilayers of amphiphilic pyrrol, artificial conjugated polymer superlattice by the potential-programmed electro-polymerization and/or electrocopolymerization, and 1-dimensional and 2-dimensional porphyrin arrays connected with conjugated and/or insulating molecular wires with P(V) porphyrin and others, for molecular photonics and electronics.

Novel 2-cyanoviologen derivatives having highly anodically shifted reduction potentials were synthesized. The colors of their cation radicals showed a variety of colors as same as those of corresponding viologen derivatives.

Several molecules having multiple regions independently responsive to stimulations have been investigated. A 2-(4-methoxyphenylazo)anthraquinone (1) having both an electrochromic quinone group and a photochromic azo group has been synthesized and its electrochromic and photochromic properties investigated. It shows interconversion of four distinct states caused by multiplication of two electrochromic redox states, quinone and hydroquinone, and two photochromic geometrical isomers, anti and syn forms. Moreover the syn-anti thermal isomerization rate of the azo region of the molecule is dependent on the state of the electrochromic quinone region. The rate for the quinone form is more than 30 times faster than that of the hydroquinone form. Additionally three other azoquinone compounds have been synthesized and investigated in the same way. The results show that these molecules have functions of multiple responsibilities for distinguishable stimulations as multi-mode chemical signal transducers.

A simple and general synthetic strategy potentially applicable for the preparation of a wide variety of unsymmetrically N,N'-bis(substituted)-4, 13-diaza-18-crown-6-ether derivatives was reported.

Novel synthesis of π-conjugated molecules by cross-metathesis reaction of vinylferrocene with a series of vinylarenes was investigated with a molybdenum-based Schrock catalyst (CHCMe2Ph)Mo(N-2,6-i-Pr2C6H3)[OCMe(CF3)2]2. The cross-metathesis reactions occurred successfully and the cross-metathesis product, i.e., heterodimers, were readily obtained selectively, together with only small amounts of the corresponding self-dimers.

A novel photochromic hexaarylbiimidazole with a bithienyl group as an extended π-conjugation unit was synthesized and the light-induced lophyl radical was found to be stabilized due to the delocalization of an unpaired electron, and to strongly absorb near-infrared light.

A simple rubbing technique to macroscopically align nanocylinders in an amphiphilic diblock liquid-crystalline copolymer is reported by Ikeda and co-workers on p. 2213. The inside cover shows highly ordered arrays of nanocylinders parallel to the rubbing direction owing to supramolecular cooperative motions between mesogens and microphase-separated domains. This opens a novel, convenient pathway for controlling defect-free nanoscopic domains over large areas.