Kazuya Uezu

Metal ion imprinted microsphere prepared by surface molecular imprinting technique using water-in-oil-in-water emulsions

A novel metal ion imprinted polymer was prepared by the surface molecular imprinting technique. Trimethylolpropane trimethacrylate (TRIM), zinc ions, and 1,12-dodecanediol-O,O′-diphenyl phosphonic acid (DDDPA) were used as the matrix-forming monomer, imprint molecule, and functional monomer, respectively. We have prepared Zn(II)-imprinted microspheres utilizing water-in-oil-in-water emulsions, which are spherically well defined and uniform. TRIM comprises of three polymerizable groups that serve to align the recognition sites produced on the polymer surface with better template effect. We conducted diagnostic zinc adsorption tests by using the Zn(II)-imprinted and unimprinted polymers in order to make an assessment on the effectiveness of TRIM-based and divinylbenzene-based imprinted polymers. The template effect of the TRIM-based polymer was enhanced by the high rigidity of the polymer matrix compared to that of the imprinted polymer whose matrix is divinylbenzene. In addition, the adsorption equilibrium constant was evaluated on the basis of the Langmuir analysis for the adsorption data. The method to prepare metal-imprinted microspheres on the surface of polymers crosslinked by TRIM is easy, and the adsorbent produced can be readily used without subsequent grinding or sieving.

Chiral-recognition polymer prepared by surface molecular imprinting technique

A highly enantioselective polymer was prepared by the surface molecular imprinting technique for the separation of optically active tryptophan methyl ester. A synthetic host molecule (phenyl phosphonic acid monododecyl ester) was proved to be effective for recognizing the chirality of amino acid esters. The l- or d-tryptophan methyl ester (TrpOMe)-imprinted polymer containing the functional host molecules revealed high enantioselectivity toward the corresponding imprinted isomer. While, the racemic-TrpOMe-imprinted and unimprinted polymers did not show the enantioselectivity at all. These results mean that the complementary binding sites such as ‘template-fit pockets’, in which the position and the alignment of the functional group in the functional host molecule are optimally adjusted for binding the corresponding imprinted isomer, are a principal factor to recognize the target molecule. These enantioselectivities were quantitatively supported by high binding constants for the corresponding imprinted isomer. To verify the recognition mechanism of the imprinted polymer, FT-IR and 1H-NMR measurement and computational modeling were conducted. Based on the results obtained, it was concluded that the enantiomeric selectivity is endowed by the electrostatic and hydrogen bonding interactions between the functional molecule and the target tryptophan methyl ester along with the chiral space formed on the polymer surface.

A molecularly imprinted polymer that shows enzymatic activity

Abstract An enzyme-mimic polymer was prepared by the surface molecular imprinting technique. In the active site of the polymer, a substrate analog was imprinted through the complex formation between a cobalt ion and alkyl imidazole that functions as the hydrolysis catalysis. The enzymatic performance of the imprinted polymer was evaluated by the hydrolysis reaction of an amino acid ester. Based on the Michaelis–Menten analysis, V max and K m were obtained. The imprinted polymer shows a high activity compared to that of the control unimprinted polymer. The result was supported by a low K m value of the imprinted polymer, indicating a high affinity to the target substrate. The enzyme-mimic polymer was found to possess a substrate specificity by using several substrates that have a different structure. A computational modeling also supports the structure of the imprinted sites formed on the polymer surface.

Metal‐imprinted microsphere prepared by surface template polymerization and its application to chromatography

A metal ion-imprinted microsphere was prepared by surface molecular template polymerization. Trimethylolpropane trimethacrylate (TRIM), zinc ions, 1,12-dodecanediol-O, O′-diphenyl phosphonic acid (DDDPA) were used as a crosslinking agent, an imprint molecule, and a functional host molecule. The Zn(II)-imprinted microspheres, which are spherically well-defined particles, were prepared by using water-in-oil-in-water (W/O/W) multiple emulsions. The combination of TRIM and DDDPA serves to align the recognition sites resulting in better template sites produced on the polymer surface. We firstly conducted diagnostic zinc- and copper-ion adsorption tests with the Zn(II)-imprinted and unimprinted microspheres in order to make an assessment on the effectiveness of the molecular imprinting technique. Further, the metal-imprinted microspheres were applied to the column operation. The separation and recovery of metals were carried out by an adsorption column packed with the Zn(II)-imprinted microspheres. This performance was compared to that of commercial chelating resins that possess similar phosphoric functional groups. The Zn(II)-imprinted polymer shows an extremely high selectivity to the imprinted zinc ions compared to that of the commercial chelating resin.

Surface imprinted polymers recognizing amino acid chirality

A highly enantioselective polymer was prepared for the separation of optically active tryptophan methylester by a surface molecular imprinting technique. An organophosphorus compound was found to be effective as a functional host molecule for recognizing the chirality of the amino acid ester. The imprinted polymers exhibited a higher template effect toward the corresponding imprinted tryptophan methylester than its isomer and analogues, while a reference polymer prepared without an imprinting molecule did not show any selectivity toward the enantiomers. The enantioselective recognition was quantitatively evaluated by determination of the binding constants of the D- and L-tryptophan methylester to the imprinted polymers. Furthermore, the mechanism for producing enantioselectivity was deduced from FTIR and 1H-NMR spectra. Based on the results obtained we concluded that the enantiomeric selectivity was mainly caused by electrostatic and hydrogen bonding interactions between the functional organophosphorus molecule and the target tryptophan methylester on the polymer surface.

Extraction of Rare Earth Metals Using Liquid Surfactant Membranes in a Mixco Extractor

The extraction of rare earth metals with liquid surfactant membranes, which contained 2-ethylhexyl-mono-2-ethylhexylphosphonic acid (PC-88A) as a carrier and sorbitan monooleate (Span 80) or L -glutamic acid dioleyl ester quaternary ammonium chloride as a surfactant, was conducted in a Mixco extractor. The concentration profile of rare earth metals along the column was measured. The experimental results were analysed by the backflow model taking into account the interfacial reaction between rare earth metals in the continuous aqueous phase and the carriers in the liquid membrane phase. The concentration profile for each of the two rare earth metals (La, Y) in a dual-component solution along the column was successively simulated by using the interfacial reaction rate constants obtained in previous batchwise experiments.

Extraction of Rare Earth Metals Using Liquid Surfactant Membranes Prepared by a Synthesized Surfactant

Abstract Three surfactants, l-glutamic acid dioleyl ester ribitol (nonionic, 2C 18Δ9 GE), l-glutamic acid dioleyl ester quaternary ammonium chloride (cationic, 2C 18Δ9 GEC 2 QA), and dioleyl dimethyl quaternary ammonium chloride (cationic, 2C 18Δ9 QA) were synthesized for potential use in liquid membrane operations. These surfactants have strongly hydrophobic, twin oleyl chains as the hydrophobic moiety. Using the synthesized surfactants, extraction of rare earth metals was carried out by liquid surfactant membranes in a stirred tank. The extraction behavior of 12 kinds of rare earth metals was systematically studied with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (commercial name: PC-88A) as a carrier. Different surfactants having an identical hydrophobic moiety can have significantly different behaviors in rare earth extractions by liquid surfactant membranes, where extraction efficiency appears to be governed by the nature of the interfacial microenvironment between oil and water. An interfac...

Radicals contributing to preirradiation graft polymerization onto porous polyethylene

Abstract Porous polyethylene hollow fiber was irradiated by an electron beam at 160 kGy and 8 kGy/min. The concentrations of the radicals such as alkyl, allyl and peroxy were determined by analyzing an integral form of ESR spectra. The comparison of the decay of the radicals with and without contact with air demonstrated that the key radical contributing to the preirradiation graft polymerization is the alkyl radical. The decay of the alkyl radical was simulated by the diffusion-controlled model in the spherical crystallites of polyethylene.

Separation of rare earth metals in a hollow-fiber membrane extractor modified by plasma-graft polymerization

Abstract A hollow-fiber membrane extractor was prepared by plasma-graft polymerization. The plasma-graft polymerization technique made it possible to modify the surface of a porous hollow-fiber membrane of poly(tetrafluoroethylene) with a polyacrylamide layer. The thickness of the layer can be controlled by the concentration of a monomer and the plasma treatment time. The surface morphology of the grafted layer was analyzed with scanning electron microscopy (SEM) and electron spectroscopy for chemical analysis (ESCA). The results of the surface analysis revealed that the grafted layer covered completely the surface of a membrane. It was confirmed that the grafted layer of polyacrylamide can adsorb rare earth metals. Separation of rare earth metals was conducted in a hollow-fiber membrane extractor modified by plasma-graft polymerization. When the surface-modified membrane was used, the separation factor of erbium to yttrium increased by the interaction between the grafted membrane and the metal ions. It was found that the hollow-fiber membrane modified by plasma-graft polymerization was very useful as a separator for rare earth metals.

Development and computational modeling of novel bifunctional organophosphorus extractants for lanthanoid separation

Novel organophosphorus extractants, which have two functional groups in the molecular structure, have been developed for the separation of lanthanoids using the liquid-liquid extraction technique. The separation efficiency and extractability of the novel extractants were investigated for nine lanthanoids. These bifunctional extractants have an extremely high extractability to all the lanthanoids compared to those of commercially available organophosphorus extractants. Two isomers having an identical chemical formulation show significantly different behaviors in lanthanoid extraction. This means that the extraction and separation abilities are quite sensitive to the structure of the spacer connecting the two functional groups. We also discuss the experimental results with a computational modeling by means of molecular mechanics and semiempirical molecular orbital methods. The novel molecular mechanics (MM) calculation program MOMEC enables us to analyze the stable conformation of a series of lanthanoid com...