Amyloid‐like Nanofibrillation of Metal‐Organic Complex Arrays Ruled by Their Precisely Designed Metal Sequences

Self‐assembly of a series of dimetallic sequences constructed on a backbone with two successive tyrosine moieties ( Fmoc‐M ¹ ‐M ² ‐CO₂H ) revealed that the resultant morphology is clearly dependent on the metal sequence, where Re‐containing sequences such as homometallic Fmoc‐Re‐Re‐CO₂H specifically afforded amyloid‐like nanofibers. These findings further allowed to achieve the fibrillation of a longer metal sequence containing three different metals ( Fmoc‐Rh‐Pt‐Re‐Re‐CO₂H ). Cyclic voltammetry of the fibrillated Fmoc‐Re‐Re‐CO₂H demonstrated that the redox activity of the metal complexes in the sequence is preserved in the nanofibrous forms.     

Reversible Pore Size Control of Elastic Microporous Material by Mechanical Force

Nanoporous materials, such as zeolites, activated carbons, and metal–organic frameworks (MOFs), are peculiar platforms in which a variety of guest molecules are stored, reacted, and/or separated. The size of the nanopores is essential to realize advanced functions. In this work, we demonstrate a very simple but innovative method for the control of nanopore size, that is, reversible and continuous control by mechanical force loaded to soft nanoporous materials. The elastic properties of several microporous materials, including zeolites, zeolite‐templated carbon (ZTC), activated carbon, and MOFs (e.g., ZIF‐8), are examined and it is found that ZTC is a material that is suitable for the aforementioned idea thanks to its extraordinary soft properties compared to the others. The original pore size of ZTC (1.2 nm) can be contracted to 0.85 nm by using a relatively weak loading force of 135 MPa, whereas the other microporous materials barely contracted. To demonstrate the change in the physical properties induced by such artificial deformation, in situ gas adsorption measurements were performed on ZTC with and without loading mechanical force, by using CO₂, CH₄, and H₂, as adsorbates. Upon the contraction by loading 69 or 135 MPa, CO₂ adsorption amount is increased, due to the deepening of the physisorption potential well inside the micropores, as proved by the increase of the heat of adsorption. Moreover, the adsorption amount is completely restored to the original one after releasing the mechanical force, indicating the fully reversible contraction/recovery of the ZTC framework against mechanical force. The experimental results are theoretically supported by a simulation using Grand Canonical Monte Carlo method. The similar adsorption enhancement is observed also on CH₄, whereas H₂ is found as an exception due to the weak interaction potential.     

Helical polyacetylenes carrying 2,2,6,6‐tetramethyl‐1‐piperidinyloxy and 2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxy moieties: Their synthesis,properties, and function

2,2,6,6‐Tetramethyl‐1‐piperidinyloxy (TEMPO)‐ and 2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxy (PROXYL)‐containing (R)‐1‐methylpropargyl TEMPO‐4‐carboxylate ( 1 ), (R)‐1‐methylpropargyl PROXYL‐3‐carboxylate ( 2 ), (rac)‐1‐methylpropargyl PROXYL‐3‐carboxylate ( 3 ), (S)‐1‐propargylcarbamoylethyl TEMPO‐4‐carboxylate ( 4 ), and (S)‐1‐propargyloxycarbonylethyl TEMPO‐4‐carboxylate ( 5 ) (TEMPO, PROXYL) were polymerized to afford novel polymers containing the TEMPO and PROXYL radicals at high densities. Monomers 1–3 and 5 provided polymers with moderate number‐average molecular weights of 8200–140,900 in 49–97% yields in the presence of (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃], whereas 4 gave no polymer with this catalyst but gave polymers possessing low M_n (3800–7500) in 56–61% yield with [(nbd)RhCl]₂‐Et₃N. Poly( 1 ), poly( 2 ), and poly( 4 ) took a helical structure with predominantly one‐handed screw sense in THF and CHCl₃ as well as in film state. The helical structure of poly( 1 ) and poly( 2 ) was stable upon heating and addition of MeOH, whereas poly( 4 ) was responsive to heat and solvents. All of the free radical‐containing polymers displayed the reversible charge/discharge processes, whose capacities were in a range of 43.2–112 A h/kg. In particular, the capacities of poly( 2 )–poly( 5 )‐based cells reached about 90–100% of the theoretical values regardless of the secondary structure of the polymer, helix and random. Poly( 1 ), poly( 2 ), and poly( 4 ) taking a helical structure exhibited better capacity tolerance towards the increase of current density than nonhelical poly( 3 ) and poly( 5 ) did. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5431–5445, 2007     

Effect of alkyl substituents structures and added ions on the phase transition of polymers and gels prepared from methyl 2‐alkylamidoacrylates

The effects of structure alteration of alkyl groups and addition of ions to solutions of new thermosensitive polymer series of poly(methyl 2‐alkylamidoacrylate)s were investigated. Potential advantages of the thermosensitive polymers are their simplicity of functionalization and transition temperature control that result from their unique α,α‐disubstituited structures. Poly(methyl 2‐propionamidoacrylate) (PMPA) and poly(methyl 2‐isobutyracrylate) (PMIBA) were thermosensitive polymers, and poly(methyl 2‐acetamidoacrylate) and poly(methyl 2‐n‐butyramidoacrylate) were completely water‐soluble and ‐insoluble, respectively. The PMIBA solution showed endotherm during the phase transition, while endotherm was not detected for PMPA. The difference between the two polymers resulted from the size of the hydrophobic groups. MPA gel was prepared by copolymerization with N,N′‐methylenebis(acrylamide) and temperature‐induced volume change of the gel was continuous. The salting‐out effect of inorganic ions on PMPA solution and MPA gel followed the Hofmeister series. The inorganic (I^? and SCN^?) and organic ions (ⁿPr₄N⁺ and ⁿBu₄N⁺), which showed the salting‐in effect, were indicated to directly interact with PMPA chains. These ions widened the temperature range of the phase transition of the PMPA solutions. This reduced cooperativity of the phase transition was caused by size decrease of cooperative domains, which resulted from the interaction of the ions with the polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4942–4952, 2005     

Palladium/copper-catalyzed sila-Sonogashira reactions of aryl iodides with alkynylsilanes via a direct C-Si bond activation

The palladium-catalyzed cross-coupling reactions of aryl iodides with alkynylsilanes in the presence of a substoichiometric amount (50 mol %) of copper(I) chloride as an activator in DMF under strictly non-basic reaction conditions afford the corresponding unsymmetrical diarylethynes in moderate to excellent yields. A wide range of substrates bearing an electron-donating or an electron-withdrawing substituent on the aromatic ring are compatible.     

Forcing under Anti‐Foundation Axiom: An expression of the stalks

We introduce a new simple way of defining the forcing method that works well in the usual setting under FA, the Foundation Axiom, and moreover works even under Aczel's AFA, the Anti‐Foundation Axiom. This new way allows us to have an intuition about what happens in defining the forcing relation. The main tool is H. Friedman's method of defining the extensional membership relation ∈ by means of the intensional membership relation ε . Analogously to the usual forcing and the usual generic extension for FA‐models, we can justify the existence of generic filters and can obtain the Forcing Theorem and the Minimal Model Theorem with some modifications. These results are on the line of works to investigate whether model theory for AFA‐set theory can be developed in a similar way to that for FA‐set theory. Aczel pointed out that the quotient of transition systems by the largest bisimulation and transition relations have the essentially same theory as the set theory with AFA. Therefore, we could hope that, by using our new method, some open problems about transition systems turn out to be consistent or independent. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pitot pressures of correctly-expanded and underexpanded free jets from axisymmetric supersonic nozzles

The structures of the axisymmetric free jets from supersonic nozzles with the exit Mach numbers of 1.5 and 2.0 are studied with special attention to the decay of the Pitot pressures downstream of the Mach disk. The Pitot pressure probe and schlieren method are used in the experiments to diagnose the flowfield. A TVD numerical method is also applied to the Euler equations, and the computed jet structures are compared with experiments. In the underexpanded jet, the experimentally obtained Pitot pressure near the jet centerline is found to substantially recover downstream of the Mach disk. By comparing the numerical computation, this phenomenon is thought to be caused by the turbulent momentum transfer to the central region from the region outside the slip line where the stagnation pressure loss is small.     

Coherence Spectrotomography of Layered Medium with White-Light Continuum

In low-coherence reflectometry, the light scattered back from a scattering medium is expected to carry information about the spectral properties of the medium as well as range information about the reflective boundaries and backscattering sites. We built and evaluated a white-light interferometry system that gives the range and spectral information about the medium using the white-light continuum. The white-light continuum gives an extremely bright and broad spectrum. Experimental results on multi-layered media are presented.     

Controlled helical orientation of carbazole in amino acid derived poly(N‐propargylamide)s

Novel L ‐alanine and L ‐glutamic acid derivatized, carbazole‐containing N‐propargylamides [N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide and N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] were synthesized and polymerized with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] (nbd = norbornadiene) as a catalyst to obtain the corresponding polymers with moderate molecular weights in high yields. Polarimetry, circular dichroism, and ultraviolet–visible spectroscopy studies revealed that both poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] took a helical structure with a predominantly one‐handed screw sense in tetrahydrofuran, CHCl₃, and CH₂Cl₂. The helix content of poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] could be tuned by heat or the addition of a protic solvent, and the helical sense of poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] was inverted by heat in CHCl₃ or in mixtures of tetrahydrofuran and CH₂Cl₂. Poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] also took a helical structure in film states. They showed small fluorescence in comparison with the monomers and redox activity based on carbazole. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 253–261, 2007