The enantioselective transport of DL-phenylalanine across a polymeric membrane plasticized with o-nitrophenyl octyl ether and containing a chiral crown ether was investigated. The transport behavior was dependent on the type of polymers. Poly (vinyl chloride) gave an excellent membrane keeping both fluxes and optical resolution ratio constant for a long time. A plasticized cellulose triacetate membrane initially showed a high optical resolution ratio, which was decreased rapidly and approached a steady value of about 7. This value was approx imately equal to those obtained with poly (vinyl chloride) membranes and supported liquid membranes. On the other hand, a plasticized cellulose nitrate membrane gave a small optical resolution ratio of less than 4 after an initial rapid decrease. The experimental results obtained with membranes of various thicknesses showed that the rate-determining step of the transport was the diffusion in the membranes.

View full abstract

Membranes having acrylic acid or sulfonate fixed charges were prepared by plasma polymerization. Acrylic acid-grafted membranes were prepared by gas phase polymerization in a plasma reactor with outer electrodes and a conjugate liquid vessel, followed by post-polymerization in the liquid phase on the microporous film of polypropylene (CG) or polyethylene (HP) as a base film. Fluorosulfonate charged-membranes were prepared by gas phase polymerization of both surfaces of the base film in a bell-jar type plasma reactor with inner electrodes, using trifluoromethane sulfonate and hexafluoropropylene. The effects of the operational conditions of plasma pressure, the RF power and the polymerization period, on the properties of a changed-membrane, grafting degree, the ion-exchange capacity, the membrane conductivity and the cation transference number, were examined experimentally. Acrylic acid-grafted membranes had high water content, and showed the high membrane conductivity. The transference number of cations of the membrane grafted on the CG film was higher than that of the membrane on the HP film. Fluorosulfonate-grafted membranes showed the resistivity lower than that of Nafion-117 membrane, and had the ion-exchange capacity competitive to that of Nafion and the high transference number of cations.

View full abstract

Transparent tough poly (vinyl alcohol) (PVA) hydrogel membranes having various water contents were prepared from 10 wt% aqueous solution of PVA and anionic poly (styrene sulfonic acid) sodium salt (NaPSS) by casting, dehydrating, and then extracting NaPSS. The oxygen permeability coefficients of these hydrogels depended on the membrane thickness, because there was an unhomogeneity of structure in the hydrogel membranes. The apparent oxygen permeability coefficient extrapolated to the infinite thickness was considered to increase with increasing radius and/or simplicity of permeable channels in the hydrogel, because the total content of free and bound waters in which oxygen is permeable was almost constant independent of the water content. The excellent oxygen permeability and transparency, and the high water absorbability of the PVA hydrogel did not change by chemical crosslinking.

View full abstract

Two series of metalloporphyrins, meso-tetra(p-sulfonatephenyl) porphine and meso-tetra (p-carboxyphenyl) porphine were prepared as their manganese-, tin-, and zinc-complexes for purpose of their fixation in polymer beads. The functions of these metalloporphyrins as an electron carrier instead of viologen derivatives and/or a photosensitizer for constructing the photoinduced hydrogen evolution system were investigated both in free and in polymer-fixed systems. Manganese- and tin-porphyrins could be photoreduced by zinc-porphyrins in the presence of electron donor, and hydrogen was generated efficiently in the system applying tin-porphyrin as an electron carrier in aqueous solutions. Among the beads-fixed heterogeneous systems, only metalloporphyrins/chitosan gel beads could act in the photoinduced hydrogen evolution system.

View full abstract

On the basis of the assumption that an equimolar mixture of 2, 4, 6-triamino-1, 3, 5-triazine derivative and barbituric acid derivative forms molecular aggregation through complementary intermolecular hydrogen bonding, two component type of organogel-forming agents were developed. The developed agents consisted of two different components and worked by the formation of intermolecular hydrogen bonding between them. Gelation test using equimolar mixtures was carried out against fourteen solvents, including soybean oil, triolein, benzene. toluene, nitrobenzene, kerosene, light oil, tetrachloromethane, chloroform, cyclohexane, N, N-dimethylformamide, 1-propanol, ethyl acetate, and acetone. It was found that equimolar mixtures of appropriate combination of 2, 4, 6-triamino-1, 3, 5-triazine derivative and barbituric acid one having long or branched alkyl chain gelled soybean oil and triolein. FT-IR spectra revealed the formation of defective hydrogen bonds between C=0 and N-H of 2, 4, 6-triaminol, 3, 5-triazine derivative and barbituric acid one. The X-ray diffraction patterns of cocrystal from acetone and triolein gel suggested the bilayered structure which was built up through intermolecular hydrogen bonding. It was assumed that the fiber-like aggegations were formed by intermolecular hydrogen bonding between 2, 4, 6-triamino-1, 3, 5-triazine derivative and barbituric acid one, then they were juxtaposed and interlocked by van der Waals interaction, finally immobilized soybean oil or triolein.

View full abstract

Konjac gels were prepared by changing the conditions (temperature and concentration of calcium hydroxide (Ca(OH)₂) and the stress growth and stress relaxation behavior of the resultant gels were determined. The correlation between preparation conditions and mechanical behavior and the difference in the behavior between the unpurified konjac and the purified konjac gels were discussed on the basis of the rigidity of the gels. The liquid crystal-formability of konjac mannan was also discussed based on optical measurements (polarized microscopy and circular dichroism). The conditions determined as optimum for preparing the konjac gels were that the temperature at 55°C and the Ca(OH)₂ concentration of 1.2-2.4 wt%. For the gels with Ca(OH)₂, the rigidity of the purified konjac gels was much higher than of the unpurified gels whereas for the gels without Ca(OH)₂, the rigidity of the unpurified gels was higher than that of the purified gels. The solid films cast from purified konjac mannan exhibited a cholesteric liquid crystalline order (left-handed) whereas the films cast from unpurified konjac showed no liquid crystalline order.

View full abstract

Pore structure-controlled silica gels were obtained by calcination (600°C, 1h in air) of silica/poly (ethyene glycol) (PEG) (50/50 wt%) composites. The molecular weight (MW) of PEG used ranged from 200 to 70000. Nitrogen adsorption isotherms of silica gels were measured at -196°C, and the pore characteristics were evaluated. When the MW of PEG was 2000, the values of the specific surface area and average pore diameter showed a maximum and a minimum of 1174 m²/g and 1.33nm. respectively. These results were explained based on the dispersion model for PEG in the composites before calcination. It was assumed that in the MW region below 2000, PEG molecules were associated while PEG molecular chains were entangled with each other in the MW region above 2000. PEG molecules having MW close to 2000 were supposed to be dispersed monomolecularly, and the pore structure of silica gels obtained reflected the structure of the composites.

View full abstract

Poly (L-glutamic acid) (PLG) membranes were prepared under an electric field (0-6400V). The effects of the electric field applied on the membrane structure and salt (LiCl, KCl) permeation were studied by scanning electron microscope (SEM) observation and permeability measurements, respectively. The SEM pictures for membranes prepared under 0V and 3000V showed that PLG domains were elongated to the direction of the electric field and at the same time the application of electric field enhanced mixing of the two domains, PLG and the crosslinker. Appreciable enhancement of the salt permeability was observed for membranes prepared under electric fields (Max. 2.5 times for LiCl), which was ascribed to reduction of tortuosity due to the observed deformation of PLG domains.

View full abstract

The vapor permeation and the pervaporation were experimented to consider a mechanism of the ethanol enrichment from the water mixture with silicone rubber. From the vapor permeation, a diffusion coefficient of water was determined as 3.3×10^-8 cm²/s which was independent of the concentration. The diffusion coefficient of ethanol depended linearly on its activity with a slope of 3.7 and its zero concentration diffusion coefficient was 3.7×10^-8 cm²/s. A calculated curve obtained by using above data, assuming the accelerated water diffusion in the presence of ethanol, agreed with the experimental data. This phenomenon influenced badly the separability of silicone rubber in this system.

View full abstract

Cellulose/poly (vinyl alcohol) (PVA) blend gel fibers were prepared by extrusion of the blend solutions in N, N-dimethylacetamide-LiCl from tubular flow field into methanol. Influences of PVA content and flow on the macroscopic orientation of cellulose in the gel fibers were examined by polarized optical microcscopy. Cellulose chains had a strong tendency to orient parallel to the gel wall. The degree of the chain orientation was much lowered with increasing PVA content. Under the lowest flow rate, with increasing PVA content, the orientational distribution deviated from longitudinal to circumferential direction. These results were attributed to influences of the interactions between the two polymers. Under the higher flow rate, all the resultant gels exhibited the larger die swell with the latter type of orientational deviation. From the observation of a PVA gel phase which remained after the treatment with the enzyme, most of PVA chains were deduced to exist as amorphous chains in the blend gel fibers.

View full abstract