Atsuomi Shundo

Epoxy resins are used in various fields in a wide range of applications such as coatings, adhesives, modeling compounds, impregnation materials, high-performance composites, insulating materials, and encapsulating and packaging materials for electronic devices. To achieve the desired properties, it is necessary to obtain a better understanding of how the network formation and physical state change involved in the curing reaction affect the resultant network architecture and physical properties.

Epoxy resins with a network structure, which are obtained by curing reactions of epoxy and amine compounds, are an important class of thermosetting resins. We here report the segmental dynamics of epoxy resins in which the three-dimensional network was well-defined and systematically varied. What we found by experiments in conjunction with atomistic molecular dynamics simulation was that when the cross-linking density in the epoxy resins increased, the glass transition temperature increased with

Until now NMR spectroscopic detection of guest chirality using an achiral host has not been possible in the absence of a chiral medium or auxiliary since chiral discrimination is principally based on chiral discrimination by host and/or diastereomeric host-guest complex formation. In this paper, we demonstrate that an achiral oxoporphyrinogen works as a host capable of signaling chiral information of alpha-hydroxycarboxylic acids in (1)H NMR spectroscopy. In particular, enantiomeric excess (ee)

Epoxy resins are composed of a three-dimensional network formed by chemical reactions between epoxy and amino compounds, which plays an important role in the mechanical properties. Thus, to use epoxy resins in various applications, it is necessary to gain a better understanding of their network structure. Here, we study the structural heterogeneity evolved in an epoxy–amine mixture during the curing process on the basis of a particle tracking technique, in which the thermal motion of probe parti

Enantioselective wetting of a chiral polymer film was demonstrated. The contact angle of chiral liquids on the film was strongly dependent on their chirality although their physical properties including surface tension were identical. Such wetting behavior resulted from the enantioselective surface reorganization involving local conformational change of the polymer chains at the liquid interface. The concept of "dynamic interface for chiral discrimination" has possible potential for the developm

In general, it has been widely accepted that the physical properties of an epoxy resin are strongly dependent on how it is prepared. However, a clear understanding of the mechanisms of the relationship at a molecular level has yet to be achieved. We here studied the glass transition dynamics and fracture behavior of four epoxy resins, which were pre-cured at different temperatures and well cured under the same conditions. Fourier-transform infrared spectroscopy revealed that the reaction kinetic

Epoxy resins are an important class of thermosetting resins, and their network structure, obtained by the curing reaction of epoxy and amine compounds, plays an important role in the material properties. We here revisited a time–temperature superposition (TTS) principle applied to the dynamic viscoelastic functions of epoxy resins, in which the network was well defined and systematically varied on the basis of the length of n-alkyl diamine. The superimposition of isothermal curves in the frequen

Epoxy resins, which possess a three-dimensional network obtained by a curing reaction between epoxy and amine compounds, are in a glassy state at room temperature. They are therefore generally brittle and exhibit rather poor resistance to crack propagation, which is one of the greatest drawbacks for their practical application. To solve this problem, a better understanding of their fracture behavior, which is related to long-term durability, is strongly desired. We herein report on how the exten

We have studied the fluorescence behavior of a dye, 6-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoic acid (NBD), in thin films of polymers with various polarities, such as poly(methyl methacrylate) (PMMA), Arton, poly(styrene) (PS), hydrogenated polystyrene (H-PS), and Zeonex. In the case of well-dispersed systems, the fluorescence behavior of NBD could be explained in terms of the mobility of the polymer matrix. This was the case for PMMA, Arton, and PS. On the other hand, when H-PS or Ze

Visualization of an acid-base equilibrium in a non-polar solvent (dichloromethane), which may be extended to other solvents, is reported. It is based on an oxoporphyrinogen as a multichromic indicator of prevailing acidity in solution and presents up to six distinct hues depending on degree of protonation, tautomeric state or presence of a basic guest.

Written in the gel: A fluoride-writable memory system has been demonstrated by using two porphyrin derivatives. Structural modification enabled both volatile and nonvolatile modes. For both porphyrins, fluorescence is quenched by addition of F(-) with only one of the derivatives returning to its initial fluorescent state following removal of F(-) (see scheme). Nonvolatile behaviour is based on anion-induced conversion from porphyrin to oxoporphyrinogen.

Heating and then cooling down a dispersion of a peptide amphiphile in water forms hierarchical fibril structures leading to a supramolecular hydrogel. When the gel was physically broken apart by shaking, it transformed into a sol state. After aging it at room temperature for a given time, it returned to the gel state (re-gelation). To obtain a better understanding of such re-gelation processes, we have applied particle tracking to the sol obtained by disrupting the gel, as a function of aging ti

Nanocellulose (NC), which consists of a bundled structure of cellulose chains, is a class of shape-anisotropic materials with a diameter of several tens of nanometers and a length of over several hundreds of nanometers. Because the production of NC is based on the extraction process from natural resources in water, NC is generally obtained in an aqueous dispersion state. Thus, an aqueous dispersion of NC can be regarded as a precursor for NC-reinforced polymer composites. The objective of this s

Non-ionic surfactant hexaethylene glycol, C(12)E(6), in water self-assembles into various kinds of mesophases by varying the surfactant concentration. A spatial heterogeneity was discussed on the basis of the diffusion of probe particles dispersed in the C(12)E(6)-water solution. Interestingly, at 50 wt% C(12)E(6) where the hexagonal structure was formed, two kinds of motion of probe particles were observed: some particles normally diffused while others were restricted, indicating the existence