Confinement of photopolymerization and solidification with radiation pressure

Controlling chemical reactions within a small space is a significant issue in chemistry, and methods to induce reactions within a desired position have various potential applications. Here we demonstrate localized, efficient photopolymerization by radiation pressure. We induced a one-photon UV polymerization of liquid acrylate solutions in the optical-trapping potential of a focused near-IR (NIR) laser beam, leading to the confinement of solidification to a minute space with dimensions smaller or equal to one-fifth of the wavelength of the NIR laser. Our approach can produce solidification volumes smaller than those achievable with conventional one-photon polymerization, thus enabling the production of tiny polymeric structures that are smaller than the diffraction limit of the trapping light. This is the first demonstration of a radiation pressure effect on a photochemical reaction.     

Evolution of packing parameters in the structural changes of silica mesoporous crystals: cage-type, 2D cylindrical, bicontinuous diamond and gyroid, and lamellar

Cage-type, two-dimensional (2D) cylindrical hexagonal (C), bicontinuous diamond (D), bicontinuous gyroid (G), and one-dimensional (1D) lamellar (L) structures of silica mesoporous crystals (SMCs) were obtained by using the anionic surfactant N-stearoyl-l-glutamic acid (C(18)GluA) as a template in the presence of the nonionic surfactant C(16)(EO)(10) (Brij-56). The mesostructures were controlled by the organic/inorganic interface curvature change induced by Brij-56. A synthesis-field diagram showed that the mesostructure changed in the sequence cage-type → C → intergrowth of C and D → intergrowth of C and G → D → G → L with increase of the amount of Brij-56. Mixed micelles were formed by the anionic and nonionic surfactants, the packing parameter g of which increased with increasing the addition amount of nonionic surfactant and the reaction temperature. The local g parameter was obtained from electron crystallography reconstruction results by calculating mean curvatures and Gaussian curvatures from the equi-electrostatic potential surface. The intergrowth of C and D and two kinds of intergrowth of C and G are also discussed.     

Oxidation of annelated diarylamines: analysis of reaction pathways to nitroxide diradical and spirocyclic products

Oxidation of diaryldiamine 2, a tetrahydrodiazapentacene derivative, provides diarylnitroxide diradical 1 accompanied by an intermediate nitroxide monoradical and a multitude of isolable diamagnetic products. DFT-computed tensors for EPR spectra and paramagnetic (1)H NMR isotropic shifts for nitroxide diradical 1 show good agreement with the experimental EPR spectra in rigid matrices and paramagnetic (1)H NMR spectra in solution, respectively. Examination of the diamagnetic products elucidates their formation via distinct pathways involving C-O bond-forming reactions, including Baeyer-Villiger-type oxidations. An unusual diiminoketone structure and two spirocyclic structures of the predominant diamagnetic products are confirmed by either X-ray crystallography or correlations between DFT-computed and experimental spectroscopic data such as (1)H, (13)C, and (15)N NMR chemical shifts and electronic absorption spectra.     

Thickening of crystals during rapid heating. II. Crosslinked polyethylene and methoxymethylated nylon 6

The effect of modification of polymer chains on crystal thickening during heating was investigated with an apparatus devised for rapid measurement of small-angle x-ray diffraction. Thickening of crystals still occurred even at a heating rate of 18°C/min in polyethylene irradiated with gamma ray doses of 30–300 Mrad, and the melting point was depressed. These results showed that the melting point depression due to irradiation is not due to a restriction on crystal thickening but rather to crystal lattice distortion. On the other hand, although methoxymethylation of nylon 6 completely inhibits crystal thickening, the melting point increases or decreases depending on the temperature of annealing preceding methoxymethylation. From these results we are led to conclude that irradiation and methoxymethylation are not effective means of obtaining the relation between melting point and crystal thickness.     

A convenient method for the synthesis of 6-enaminopurine derivatives by catalytic hydrogenation of 6-cyanomethylenepurines

6-Cyanomethylenepurines have been catalytically hydrogenated to the corresponding α-(aminomethylene)purine-6-acetic acid derivatives in good yields using dimethylformamide-benzene as solvent over Pd-C under medium pressure.     

Effects of carbon filler on sorption and diffusion of gases through rubbery materials

Effects of carbon filler on the sorption and diffusion of carbon dioxide in natural rubber and in styrene-butadiene rubber have been studied. Sorption isotherms conform to Henry's law in unfilled rubber and to Langmuir's law in carbon black. The isotherms in filled rubber exhibit a combination of the two sorption modes. The Henry's law solubility parameter k_D increases with carbon filler content; the Langmuir saturation constant C′_A initially is constant with filler level, but then decreases abruptly when carbon particles begin to aggregate. The diffusion coefficient decreases with increasing filler content, presumably owing to geometric effects and to polymer chain immobilization in the interfacial regions.     

Magnetic properties of H+ implanted bubble garnet films by means of depth selective conversion electron Mössbauer spectroscopy

Bubble garnet films before and after 50 keV H⁺ implantation have been studied by means of DCEMS. The spintilt angle of the films as grown after etching off 1000 å was measured to be 30±2? relative to the surface normal at the top of the surface. The doses of implanted H⁺ ions were 2, 4 and 8×10¹⁶ ions/cm². Mössbauer spectra were measured after successive etching of the implanted layer. The magnetic hyperfine field was obtained as a function of depth. The implanted hydrogen distribution was also measured by the¹H(¹⁵N, αγ)¹²C reaction.     

Cyano-bridged Mn(III)3M(III) (M(III) = Fe, Cr) complexes: synthesis, structure, and magnetic properties

Two cyano-bridged tetranuclear complexes composed of Mn(III) salen (salen = N,N'-ethylene bis(salicylideneiminate)) and hexacyanometalate(III) (M = Fe, Cr) in a stoichiometry of 3:1 have been selectively synthesized using {NH2(n-C12H25)2}3[M(III)(CN)6] (M(III) = Fe, Cr) starting materials: [{Mn(salen)(EtOH)}3{M(CN)6}] (M = Fe, 1; Cr, 2). Compounds 1 and 2 are isostructural with a T-shaped structure, in which [M(CN)6]3- assumes a meridional-tridentate building block to bind three [Mn(salen)(EtOH)]+ units. The strong frequency dependence and observation of hysteresis on the field dependence of the magnetization indicate that 1 is a single-molecule magnet.     

Crystallinity of bulk polyacetylene

The fine structure of bulk trans-polyacetylene (PA) was investigated by x-ray diffraction. The degree of crystallinity 0.81, determined by Ruland's method, was significantly higher than the value for linear polyethylene. The disorder parameter k was 5, which is much larger than the value for polyethylene. These results led us to propose that PA crystals are more disordered than PE crystals owing to the higher rigidity of PA chains. Small-angle x-ray diffraction indicated that the crystal morphology is of the extended-chain type rather than lamellar. All results obtained in this work showed that the fine structure of PA bulk is such as to facilitate electrical conduction of bulk PA.     

Effects of extension on the gas permeability of hard elastic polypropylene film

Permeabilities of He, N₂, O₂, Ar, and CO₂ in stretched hard-elastic polypropylene film exhibiting extraordinarily high elasticity were measured as functions of temperature, pressure, and extension ratio. The permeability decreases slightly for strains of 10% or less, increases abruptly for strains from 15% to 30%, and then increases gradually for strains up to 100%. In recovery from extension, changes in permeability are similar to those in extension. The gas permeation mechanism is of the solution-diffusion type for extensions less than 15%. Above 15% extension, the mechanism involves permeation through voids created during deformation. The apparent mean pore size, estimated from the gas permeation, is very large at comparatively small extensions, and decreases with increasing extension. The change in specific volume accompanying extension of the sample indicates that only a very small fraction of the voids are interconnected to form channels that traverse the thickness of the film.