Investigation on the Surface‐Confined Self‐Assembly Stabilized by Hydrogen Bonds of Urea and Amide Groups: Quantitative Analysis of Concentration Dependence of Surface Coverage

Formation of a hydrogen‐bond network via an amide group is a key driving force for the nucleation–elongation‐type self‐assembly that is often seen in biomolecules and artificial supramolecular assemblies. In this work, rod‐coil‐like aromatic compounds bearing an amide ( 1 a – 3 a ) or urea group ( 1 u – 3 u ) were synthesized, and their self‐assemblies on a 2‐D surface were investigated by scanning tunneling microscopy (STM). According to the quantitative analysis of the concentration dependence of the surface coverage, it was revealed that the strength of the hydrogen bond (i.e., amide or urea) and the number of non‐hydrogen atoms in a molecular component (i.e., size of core and length of alkyl side chain) play a primary role in determining the stabilization energy during nucleation and elongation processes of molecular ordering on the HOPG surface.     

Polymeric Electron Carriers

Polymers containing 1,4-dihydronicotinamide (P-NAH) alloxan (P-A), and viologen (P-V²⁺) moieties were synthesized and characterized. P-NAH reduced various organic substances such as lipoic acid, alloxan, and viologens and also immobilized quinone mediated by alloxan. P-A was reduced to the polymer-bearing alloxan radical and the dialuric acid structure without crosslinks by one- and two-electron reduction, respectively, and P-A also mediated the redox reaction occurring between aqueous and organic (water-immiscible) layers. P-V²⁺ was converted to the stable viologen radical reversibly by one-electron reduction. Electric potentials and currents on photo-reduction of P-V²⁺ and catalytic behavior of P-V²⁺ in the reduction of carbonyl compounds were examined.     

Thermal behavior and dismantlability of adhesives containing various inorganic salts

As a fundamental study on the development of dismantlable adhesives containing chemically reactive materials, the thermal behavior and dismantlability of an epoxy adhesive containing one of the twenty-seven inorganic salts (chlorides, perchlorates, and nitrates) were observed. In the thermal behavior measured by the differential scanning calorimetry, epoxy adhesives with inorganic salts containing iron, copper, zinc, and aluminum cations released heats of reaction at lower temperatures than the adhesive alone or the adhesives with other inorganic salts. Since such inorganic salts were considered to be effective candidates as fillers in dismantlable adhesives, the adhesion strengths of their mixtures with the adhesive were observed after heat aging at 270 °C for 30 min. The results showed that both chloride and perchlorate salts specifically decreased the adhesion strength after heating. On the other hand, the effect of nitrate salts on the decrease in adhesion strength was low in comparison with the chloride and perchlorate salts.     

Application of 28Mg to the kinetic study of Mg uptake by rice plants

The time course of Mg uptake and release using intact rice plants and ²⁸Mg as a tracer is presented. Since there is no conventional Mg tracer available, ²⁸Mg was produced via ²⁷Al(α, 3p)²⁸Mg reaction using a cyclotron. Using the purified ²⁸Mg tracer, it was found that the uptake amount of ²⁸Mg by the rice plants increased linearly during 30 min of application. After ²⁸Mg treatment for 90 min, the roots were sequentially washed with iced solution for 120 min. Within about 10 min, almost all of the ²⁸Mg, that was thought to be weakly bound to the apoplast, was washed away.     

Biodegradable Polyurethanes from Plant Components

Abstract

Polyurethane (PU) sheets and foams having plant components in their network were prepared by using the following procedure. Polyethylene glycol (PEG) was mixed with one of the following; molasses, lignin, woodmeal, or coffee grounds. The mixture obtained was reacted with diphenylmethane diisocyanate (MDI) at room temperature, and precured PUs were prepared. The precured PUs were heat-pressed and PU sheets were obtained. In order to make PU foam, the above mixture was reacted with MDI after the addition of plasticizer, surfactant (silicone oil), catalyst (di-n-butyltin dilaurate), and droplets of water under vigorous stirring. The glass transition temperature, tensile and compression strengths, and Young's modulus of the PU sheets and foams increased with an increasing amount of plant components. This suggests that saccharide and lignin residues act as hard segments in PUs. It was found that the PUs obtained were biodegradable in soil. The rate of biodegradation of the PUs derived from molasses and coffee grounds was between that of cryptomeria (Cryptomeria japonica) and beech (Fagus sieboldi).