Preparation of novel fluoroalkyl end-capped oligomers/silica hybrid nanoparticles-encapsulation of a variety of guest molecules into fluorinated nanoparticles

Fluoroalkyl end-capped oligomers reacted with tetraethoxysilane and silica/nanoparticles under alkaline conditions to afford fluoroalkyl end-capped oligomers/silica nanoparticles (mean diameters: 31–54 nm) with a good dispersibility and stability in organic media. Interestingly, the isolated fluorinated particle powders were found to afford nanometer size-controlled colloidal particles with a good redispersibility and stability in these media. In addition, fluoroalkyl end-capped oligomers/silica nanoparticles-encapsulated guest molecules such as stable organic radicals and ionic liquids were prepared under similar conditions. These fluorinated nanoparticles-encapsulated guest molecules were applied to a new type of surface-modification agent, and these particles were able to disperse well above the poly (methyl methacrylate) films.     

Synthesis of chiral nonracemic 1-(2-pyridinyl)ethylamines: stereospecific introduction of amino function onto the 2-pyridinylmethyl carbon center

Stereospecific substitutions of optically pure 1-(pyridinyl)ethyl methanesulfonates with various amines are described. The reaction of (R)- or (S)-1-(2-pyridinyl)ethyl methanesulfonate with primary amines, including amino acid esters, gives N-substituted (S)- or (R)-1-(2-pyridinyl)ethylamines (4) with inversion of the configuration. Secondary cyclic amines are also reacted with (R)-2 to give the corresponding substituted amines (5) in excellent yields. Optically pure and meso triamine ligands having two pyridine rings, (S,S)-4f and meso-4f, (S,S)-9e, (S,R)-9e, and (S,S)-9f, have been prepared in stereochemically pure form by this method. Not only the substitution reaction of optically active 2 but also that of 1-(4-pyridinyl)ethyl and 1-(3-pyridinyl)ethyl methanesulfonates 11 and 14 take place stereospecifcally with inversion of the chiral center.     

The Singular Homology of the Hawaiian Earring

The singular homology groups of compact CW-complexes are finitelygenerated, but the groups of compact metric spaces in generalare very easy to generate infinitely and our understanding ofthese groups is far from complete even for the following compactsubset of the plane, called the Hawaiian earring: Griffiths [11] gave a presentation of the fundamental groupof H and the proof was completed by Morgan and Morrison [15].The same group is presented as the free -product of integers Z in [4, Appendix]. Hence the firstintegral singular homology group H₁(H) is the abelianizationof the group . These results have been generalized to non-metrizable counterparts H_I of H(see Section 3). In Section 2 we prove that H₁(X) is torsion-free and H_i(X) =0 for each one-dimensional normal space X and for each i 2.The result for i 2 is a slight generalization of [2, Theorem5]. In Section 3 we provide an explicit presentation of H₁(H)and also H₁(H_I) by using results of [4]. Throughout this paper, a continuum means a compact connectedmetric space and all maps are assumed to be continuous. Allhomology groups have the integers Z as the coefficients. Thebouquet with n circles is denoted by B_n. The base point (0, 0) of B_n is denoted by o forsimplicity.     

Finite sheeted covering maps over 2-dimensional connected, compact Abelian groups

Let G be a 2-dimensional connected, compact Abelian group and s be a positive integer. We prove that a classification of s-sheeted covering maps over G is reduced to a classification of s-index torsionfree supergroups of the Pontrjagin dual . Using group theoretic results from earlier paper we demonstrate its consequences. We also prove that for a connected compact group Y:

(1)

Every finite-sheeted covering map from a connected space over Y is equivalent to a covering homomorphism from a compact, connected group.

(2)

If two finite-sheeted covering homomorphisms over Y are equivalent, then they are equivalent as topological homomorphisms.

     

Xylene-stream method for obtaining thin polyethylene specimens for electron microscopy

A new technique is described for obtaining thin specimens from melt-crystallized polyethylene surface for studying the lamellar structure with the electron microscope. The specimen was first backed with carbon–gelatin backing and then the polyethylene side was exposed to a temperature-controlled xylene stream. After dissolving most of the specimen, a very thin layer of polyethylene which shows certain aspects of the original lamellar structure was obtained. Stereoscopic micrographs revealed the structure of polyethylene consisting of curved layers, concave, convex and other forms. These curved layers were identified by analysis of the Bragg fringes to be the crystalline lamellae. A special pattern resembling a spider in shape caused by a spherical crystal was investigated.