Rodlike macromolecules through spatial overlapping of thiophene dendrons.

Two novel dendritic macromonomers 7 and 8 functionalized with electroactive conjugated thiophene oligomers were synthesized by stepwise cross-coupling reactions and the introduction of a vinyl group at the focal point. Both macromonomers were polymerized into dendronized polymers 9 and 10 by using a radical polymerization method. The photophysical and redox behaviors of dendronized polymers 9 and 10 are significantly different from those of the corresponding macromonomers. This difference may result from the spatial overlapping of thiophene dendrons through π-π interactions when the dendrons are connected to a polymer backbone. The dendronized polymers can organize into large-area two-dimensional sheets with a thickness of 4.8 nm. Polymer 9, which has all-dendritic thiophene side chains, exhibited enhanced conductivity by partial doping with iodine or nitrosonium tetrafluoroborate (NOBF(4)). The novel amphiphilic dendronized polymer 15 was synthesized by the atom-transfer radical polymerization of macromonomer 7 from a poly(ethylene glycol) (PEG) macroinitiator and was found to have a self-organized structure in water.

Macroporous conductive polymer films fabricated by electrospun nanofiber templates and their electromechanical properties.

We demonstrate a facile method to fabricate macroporous poly (3,4-ethylenedioxythiophene)/poly (4-styrene sulfonate) (PEDOT/PSS) films with empty channels by using electrospun nanofiber as a sacrificial template. The channels within the PEDOT/PSS films were prepared by depositing PEDOT/PSS aqueous dispersion onto poly (vinyl pyrrolidone)/poly(methyl methacrylate) (PVP/PMMA) nanofiber template, and then the nanofibers were removed by solvent extraction. The average diameter of the channels is 313±45 nm, which is almost the same as the parent PVP/PMMA nanofibers. The macroporous PEDOT/PSS film with the empty channels showed an enhancement of electromechanical properties compared to the nonporous PEDOT/PSS film.

Intramolecular axial ligation of zinc porphyrin cores with triazole links within dendrimers.

Stable ligation: A series of dendritic porphyrins, such as that depicted in which benzyl ether dendrons were linked to a porphyrin core through 1,2,3-triazole links, was synthesized. Absorption and fluorescence spectra showed a stable axial ligation at the zinc center of the porphyrin core by triazole links in dendritic wedges and indicated that the position of the triazole links strongly affected the stability of the axial ligation within the dendrimer.A series of dendritic porphyrins 7-9 and 12, in which benzyl ether dendrons were linked to a porphyrin core through 1,2,3-triazole links, were synthesized by Cu(I)-catalyzed cycloaddition of azides and alkynes. Absorption and fluorescence spectra showed a stable axial ligation at the zinc center of the porphyrin core by triazole links in dendritic wedges and indicated that the position of the triazole links strongly affected the stability of the axial ligation within the dendrimer. When the porphyrin core was surrounded by aryl ether dendrons having anionic termini and triazole linkers, a significant rate enhancement for photoinduced electron transfer was observed compared with a similar water-soluble dendritic zinc porphyrin lacking triazole linkers. These triazole links constituted a direct pathway within the dendrimer architecture for electron transfer between the zinc porphyrin core and peripheral electron acceptors.

Fabrication of TiO2 using L-lysine-based organogelators as organic templates: control of the nanostructures.

Using uncharged or negatively charged L-lysine-based organogelators as templates, the nanostructures of TiO2 are controllable.

Preparation of helical nanostructures using chiral cationic surfactants.

Left-handed helical short nanotubes and mesoporous nanofibers were prepared by sol-gel transcription using a new chiral cationic surfactant.

Nanofiberization of inner helical mesoporous silica using chiral gelator as template under a shear flow.

Aligned nanofibers with inner-helical mesoporous silica were synthesized using chiral gelator as template under basic conditions and a shear flow.

Cellular interactions and degradation of aliphatic poly(ester amide)s derived from glycine and/or 4-amino butyric acid.

A series of poly(ester amide)s derived from amino acid (glycine or 4-amino butyric acid), diol (1,6-hexanediol or 1,4-butanediol) and sebacoyl chloride were prepared by interfacial polymerization. FT-IR analysis indicated that for poly(ester amide)s derived from glycine, only amide-amide hydrogen bonds and hydrogen-bonded C=O ester groups were established, whereas the poly(ester amide)s derived from 4-amino butyric acid contained amide-amide hydrogen bonds and amide-ester hydrogen bonds, including NH groups and C=O ester groups in free state. The biodegradability was estimated by weight residue of poly(ester amide) films in pH 6 buffer solution with papain at 37 degrees C. The poly(ester amide) films derived from glycine demonstrated significantly improved degradability compared to the poly(ester amide) films derived from 4-amino butyric acid. This difference of degradation rate could be explained by the bonding state in C=O ester groups. The cellular interaction of the poly(ester amide)s was studied by measuring the proliferation of human dermal fibroblasts on the polymer films. The cells proliferated significantly faster on poly(ester amide) films derived from 4-amino butyric acid than on poly(ester amide) films derived from glycine. These results suggest that the poly(ester amide) prepared in this study may serve as a potential cell-compatible biomedical material.

Novel family of low molecular weight hydrogelators based on L-lysine derivatives.

New L-lysine derivatives with a positively charged terminal can gel water below 1 wt%; particularly, 1a and 2a form a hydrogel at 0.3 wt% corresponding to approximately 12,300 and 12,500 waters/gelator molecule, respectively.

Preparation of organic-inorganic composites containing rod-like phthalocyanine polymers.

Sol-gel polymerization of tetraethoxysilane in the presence of amphiphilic phthalocyanine polymer 2 produced organic-inorganic composites with the rod-like phthalocaynine polymers incorporated within ordered hexagonal channels.

Site-selective electroless nickel plating on patterned thin films of macromolecular metal complexes.

We demonstrate a simple route to depositing nickel layer patterns using photocross-linked polymer thin films containing palladium catalysts, which can be used as adhesive interlayers for fabrication of nickel patterns on glass and plastic substrates. Electroless nickel patterns can be obtained in three steps: (i) the pattern formation of partially quaterized poly(vinyl pyridine) by UV irradiation, (ii) the formation of macromolecular metal complex with palladium, and (iii) the nickel metallization using electroless plating bath. Metallization is site-selective and allows for a high resolution. And the resulting nickel layered structure shows good adhesion with glass and plastic substrates. The direct patterning of metallic layers onto insulating substrates indicates a great potential for fabricating micro/nano devices.

Conductive nanoscopic fibrous assemblies containing helical tetrathiafulvalene stacks.

Tetrathiafulvalenes (TTF) S-TTF and R-TTF having four chiral amide end groups self-organize into helical nanofibers in the presence of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-quinodimethane (F(4)TCNQ). The intermolecular hydrogen bonding among chiral amide end groups and the formation of charge-transfer complexes results in a long one-dimensional supramolecular stacking, and the chirality of the end groups affects the molecular orientation of TTF cores within the stacks. Electronic conductivity of a single helical nanoscopic fiber made of S-TTF and F(4)TCNQ is determined to be (7.0+/-3.0)x10(-4) S cm(-1) by point-contact current-imaging (PCI) AFM measurement. Nonwoven fabric composed of helical nanofibers shows a semiconducting temperature dependence with an activation energy of 0.18 eV.

Wrapping of self-organized fluorescent nanofibers with a silica wall.

Amphiphilic compounds 1 and 2, composed of an aromatic pyrene core and an amphiphilic three-branched unit, were synthesized and investigated for their self-organizing process in solution by UV-vis, fluorescence spectra, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and fluorescence microscopes. While 2 formed spherical objects in a mixed solvent of methanol and water, 1 assembled into long, flexible, and fluorescent fibers through pi-pi stacking of pyrene cores and hydrogen bonding among amide groups. The fluorescence spectra and morphologies strongly depended on the concentration and solution temperature. The fibrous assemblies were wrapped with an ultrathin silica wall by the acidic sol-gel polymerization of tetraethoxysilane (TEOS). A transmission electron microscopy (TEM) image after the sol-gel polymerization showed discrete fibrous structures with a uniform diameter of 3.5 nm and several micrometers in length. The thickness of the silica wall and the inner diameter of one fiber were estimated to be 0.5 nm and 2.5 nm, respectively. The observed inner diameter of the fiber was almost compatible with the width of the cylindrical assembly made of 1. The pyrene unit in 1 can interact with the sidewall of single-walled carbon nanotubes (SWNTs) through pi-pi interaction, and the adsorption of 1 onto the surface of SWNTs could disrupt the formation of bundles. The accumulation of oligomeric silica species at the hydrophilic surface created organic-inorganic nanoscopic fibers containing electronic conductive SWNTs.

Organogelation by polymer organogelators with a L-lysine derivative: formation of a three-dimensional network consisting of supramolecular and conventional polymers.

Polymer compounds consisting of a L-lysine derivative and conventional polymers, such as poly(ethylene glycol), polycarbonate, polyesters, and poly(alkylene), have been synthesized and their organogelation properties examined in various solvents. These polymer compounds function as good organogelators that form organogels in many organic solvents and oils. The organogelation ability is almost independent of the polymer backbone. Observation by field-emission scanning electron microscopy (FE-SEM) demonstrates that the polymer organogelators form a supramolecular polymer with a diameter of several tens of nanometers and create a three-dimensional network in organogels. FT-IR spectroscopic analysis shows that the supramolecular polymer is mainly formed by the self-assembly of L-lysine segments through hydrogen-bonding and van der Waals interactions. Furthermore, the organogels formed by the polymer organogelators have a lower gel-sol temperature and higher gel strength than those of a low-molecular-weight model organogelator.

Control of mesoporous silica nanostructures and pore-architectures using a thickener and a gelator.

A chiral cationic thickener l-ValPyBr, which was able to enhance the viscosity of water and form loosely physical gel in mixtures of water and alcohols, was synthesized. Sol-gel polymerization of TEOS was carried out in mixtures of water and alcohols under basic conditions using the self-assemblies of l-ValPyBr as template. The left-handed twisted mesoporous silica nanoribbons, which were constructed by nanotubes in monolayer, were obtained, and they tended to self-assemble into bundle structure. Stirring under the preparation process played an important role in the formation of this bundle structure. The obtained silica nanoribbons were uniform in width, thickness, and helical pitch without combining amorphous particles. The helical pitch and pore size of the mesoporous silica nanoribbons sensitively depended on the volume ratio of alcohols to water in the reaction mixtures. With increasing volume ratio of alcohols to water in the reaction mixture, the morphologies of the obtained silica changed from left-handed twisted ribbon to coiled ribbon, then to tubular structure. A compound l-ValPyPF6, structurally related to thickener l-ValPyBr, was able to form physical gel in ethanol, THF, acetonitrile, and the mixtures of ethanol and water. Left-handed multiple helical mesoporous silica nanofibers were prepared by using the self-assemblies of l-ValPyPF6 as template in mixtures of water and alcohols under basic conditions. By controlling both the volume ratio of ethanol to water and the weight ratio of l-ValPyPF6 to TEOS, two- or three-dimensional pore-architecture constructed by porous chiral nanotubes was obtained.

Self-organization of low-symmetry adjacent-type metallophthalocyanines having branched alkyl chains.

Low-symmetry, adjacent-type metallophthalocyanines 1 and 2 with four branched alkyl chains on one side and a chiral bridging segment on the other were synthesized, and their self-organization properties were investigated. The synthesized adjacent-type phthalocyanines were liquid-crystalline and exhibited a phase transition from the crystalline phase to the mesophase below room temperature. X-ray diffraction indicated that the molecules are stacked in one-dimensional columnar aggregates with a hexagonal arrangement. The self-organization behavior of zinc complex 1 and cobalt complex 2 was also investigated with a monolayer experiment at the air-water interface. The adjacent-type phthalocyanines formed a stable monolayer at the air-water interface, and the monolayers could be transferred onto quartz substrates by a Y-type deposition. UV-vis, XRD, and CD measurements for the resulting Langmuir-Blodgett films indicated that 1 and 2 had different molecular orientations.

l-Lysine-based supramolecular hydrogels containing various inorganic ions.

The preparation of supramolecular hydrogels containing various inorganic acids and salts using L-lysine-based hydrogelators is conducted and their thermal stabilities, gel strengths, FT-IR spectra, and electron micrographs are measured. These hydrogelators can form supramolecular hydrogels over a wide pH range and contain inorganic acids and salts. The supramolecular hydrogels based on ester-type hydrogelators have good thermal stabilities (high Tgel), while the hydrogelator with a carboxyl group forms a thermally sensitive gel with high mechanical strength. Furthermore, the gelation mechanism is discussed using FT-IR spectroscopy and TEM observations.

Specialist gelator for ionic liquids.

Cyclo(l-beta-3,7-dimethyloctylasparaginyl-L-phenylalanyl) (1) and cyclo(L-beta-2-ethylhexylasparaginyl-L-phenylalanyl) (2), prepared from L-asparaginyl-L-phenylalanine methyl ester, have been found to be specialist gelators for ionic liquids. They can gel a wide variety of ionic liquids, including imizazolium, pyridinium, pyrazolidinium, piperidinium, morpholinium, and ammonium salts. The mean minimum gel concentrations (MGCs) necessary to make gels at 25 degrees C were determined for ionic liquids. The gel strength increased at a rate nearly proportional to the concentration of added gelator. The strength of the transparent gel of 1-butylpyridinium tetrafluoroborate ([C(4)py]BF(4)), prepared at a concentration of 60 g L(-1) (gelator 1/[C(4)py]BF(4)), was ca. 1500 g cm(-2). FT-IR spectroscopy indicated that a driving force for gelation was intermolecular hydrogen bonding between amides and that the phase transition from gel to liquid upon heating was brought about by the collapse of hydrogen bonding. The gels formed from ionic liquids were very thermally stable; no melting occurs up to 140 degrees C when the gels were prepared at a concentration of 70 g L(-1) (gelator/ionic liquid). The ionic conductivities of the gels were nearly the same as those of pure ionic liquids. The gelator had electrochemical stability and a wide electrochemical window. When the gels were prepared from ionic liquids containing propylene carbonate, the ionic conductivities of the resulting gels increased to levels rather higher than those of pure ionic liquids. The gelators also gelled ionic liquids containing supporting electrolytes.

Self-organization of supramolecular complex composed of rigid dendritic porphyrin and fullerene.

A second-generation 1,3,5-phenylene-based dendritic porphyrin decorated with flexible alkyl chains exhibited a liquid crystallinity, and the inclusion of fullerene within the nanospace of the dendritic porphyrin strongly affected the mesophase structure in the thermotropic liquid-crystalline phase.

Preparation of helical transition-metal oxide tubes using organogelators as structure-directing agents.

We prepared novel transition-metal (Ti, Ta, V) oxide fibers with chiral, helical, and nanotubular structures. The nanostructured metal oxide materials were provided by the sol-gel polymerization of metal alkoxides using chiral self-assemblies of organogelators as structure-directing agents. The chiral structures of the metal oxide fibers can be created by the formation of chiral self-assemblies constructed by organogelators and the transcription of the organogel superstructure into metal oxides.