Our study on gas transport properties of polyphosphazenes and poly (vinyl exters) was reviewed. The purpose of this study is to accumulate our knowledge on the relationships between structure and gas transport of both rubbery and glassy polymers.
Gas permeability of polyphosphazenes largely depends on the structures of side chain. When the side chain is small and nonpolar, the permeability reaches to the order of 10^-8 cm³ (STP) ·cm/ (cm² · sec ·cmHg). The permeability decreased about two orders for some gases as the increase of size and/or polarity of the side chain and it was mainly due to the decrease of diffusivity. For poly [bis (trifluoroethoxy) phosphazene]. it was shown that gas dissolves and diffuses into the mesophase above T (1). In addition, specific interactions between fluorine containing group and polar gases was shown.
Form the study of poly (vinyl esters), gas permeability in glassy state was increased by introduction of rigid and bulky groups. This result is in contrast to that of rubbery polymers, polyphosphazenes. Gas diffusivity at Tg was tried to quantitatively correlate with free volume for all poly (vinyl esters) studied. From CO₂ sorption study, plasticization effect of sorbed gas was revealed. Modifications of dual-mode sorption model and a new model considering this effect were briefly reviewed together with a totally different transport model, “pore” model.

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Further studies have been made on a theory on solute transport through a membrane proposed recently by us which predicts two relaxation processes with the slower rate P₁ and the faster rate P₂ under quasi-steady state conditions. We elucidate the dependence of P₁ and P₂ upon the volume fractions of the donor, receiver and membrane phases. It is shown that P₁ and P₂ have extrema when the volume fraction of the donor and receiver phases are equal ;P₂ has a minimum but P₁ may have either maximum or minimum. We also derive simple approximate formulas for the time course of the solute concentrations in the respective phases.

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The separation of oxygen from gas mixtures of oxygen and nitrogen with a liquid membrane system supported by microporous polypropyrene membrane (Celgard) with [N, N'-bis (salicylidene) dipropylenetriamine] cobalt (II) as the carrier was examined. when the 1 : 1 mixture of dimethylsulfoxide and dimethylacetamide was used as the diluent solvent, the maximum oxygen content of 79% was obtained with this liquid membrane system. The initial permeation flux was well explained by the transport mechanism with a reversible instantaneous reaction. The degradation of the permeation rate was observed which was caused by the irreversible oxydation reaction of the carrier. It was demonstrated that the renewal of the membrane phase is effective for the recovery of this degradation.

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Chitosan membranes for ultrafiltration were prepared by casting acetic acid solutions of chitosan including an each amount of polyethylene glycol (PEG) as additives. Additives were eliminated by elution in hot water after the neutralization of membrane. The water flux of the membrane was measured and the membrane structure was observed by the scanning electron microscope. The membrane was found to consist of three layers ; the surface, the internal microporous layer and the opposite surface. With increasing the amount of PEG from 25 phr to 100 phr at the membrane preparation, the water flux increased largely more than 1000 folds, but there was only a 10% increase in the degree of hydration, H, of the membrane. The drastic change in the macroscopic membrane structure occured in the vicinity of H = 0.7, i.e., the micropores which penetrated throughout the membrane were formed in the region H>0.7. The molecular weight of PEG also affected the membrane structure and the water flux.

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Chitosan membranes for ultrafiltration were prepared by casting acetic acid solutions of chitosan including polyethylene glycol (PEG) as an additive. The additive was eliminated by elution in hot water after the neutralization of membrane. The ultrafiltration through the chitosan membrane was carried out using the solutions of proteins such as bovine serum albumin and γ-globulin. It was found that the rejection of proteins depended on the pH of the solution and it changed drastically in the vicinity of the pH of the isoelectric point of the protein (pH_I ). The high rejection was observed at the pH lower than the pH, and the rejection was no longer observed beyond the pH_I. These facts mean the interaction between the membrane charge and the protein.
The permeation rate of the solution was kept constant in the pH region more than pH 6 but it largely decreased in the lower pH region. It was considered from the SEM observations that the chitosan membrane was partially desolved in the low pH buffer solution and at the same time some micropores which had existed on the air-side surface disappeared and became the dense layer.
In addition, it was recognized that an appropriate membrane structure was required for the charged ultrafiltration membrane.

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Polymers containing amino group were investigated to be used as biomaterials. Amination of polystyrene was carried out two steps ; nitration by nitric acid and acetic anhydride in carbon tetrachloride, and then reduction of nitro group with tin (II) chloride. The degree of nitro group introduced in polystyrene can be controlled by adjusting the amount of nitric acid. Then the solubility of these polymers in organic solvents was examined, and the processability of membrane prepared using the solution casting method was evaluated. The conditions of membrane preparation, e. g. the time of solvent evaporation, polymer concentration in the solution and the kind of coagulating solvents, affected to the physical structure of the membrane. Each membrane prepared was that of spongy structure entirely. Thus, these membranes are expected to be applied as biomaterials, e. g. antithrombogenic membrane by immobilization of heparin and membrane reactor with enzymes.

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We have examined static responses of Millipore membranes infiltrated with only dioleyl phosphate (DOPH), DOPH and dioleoyl phosphatidylethanolamine (DOPE), and DOPH and cholesterol to a bitter (strychnine sulfate), a sour (HCl), a salty (NaCl) and a sweet (sucrose) substances. The DOPE-mixed membrane responded more sensitively to HCl. The cholesterol-mixed membrane responded more sensitively to strychnine, NaCl and sucrose. The present results are similar to the assumption that all sensory cells do not respond uniformly to a chemical substance in the biological system because of a difference of the membrane composition of sensory cells.

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Composite oxygen separating membrane containing stable oxygen carrier in high concentration was developed.
The “picket fence” porphyrin (Co P), was selected as the oxygen carrier because its steric hindrance group is expected to protect the vacant site for oxygen binding, and also is expected to act as the barrier against the inactivation by dimerization.
The coordination properties of Co P complexed with various polymeric ligand was studied, to prove that, in the solid membrane, only active five-coordinate complex was exclusively formed.
We also found that the highly purified Co P shows the high stability against oxygen for several months in the solid membrane of the polymeric ligand.
In order to obtain the high selectivity of oxygen even at the high upstream oxygen pressure, the high concentration of the carrier in the membrane is required.
However, the membrane with the high carrier concentration is too brittle for the practical use. The strength of the membrane might be improved by forming the composite on the porous support. But every attempt to form the composite of the thin active layer on the organic porous membranes result in the formation of composite membrane with low oxygen selectivities.
Our investigation revealed that if active layer with the high carrier concentration was formed on the surface of the specific porous glass membrane, the composite membrane can afford the high oxygen selectivity (αO2N2=16), even at the high upstream pressure of the oxygen (76 cmHg).

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We intended to propose a novel ultrafiltration method using BMM for determination of virion size in solution and for evaluation of the size of aggregate being composed of several virions and content cocurrently. We assumed that the pore structure of BMM was represented by multilayer structure and consequently multi-step ultrafiltration occured and that BMM did not adsorb protein and removing virions was determined only by the geometrical sizes of virion and pore. The equation derived theoretically was
Φ= (0.5d/2.303) (2v/2r_f) C'-D (1) where Φ is the virus logarithmic rejection coefficient and, d, 2v and 2r_f are membrane thickness, particle size and mean pore size, respectively, and C' and D are constants. The reliability of eq 1 was proved experimentally using gold particles with various sizes and Japanese encephalitis virus (JEV). The values of C' and D for JEV were nearly constant for BMMs with various 2r_f. The sizes of the aggregates of Φx 74 virions and Hepatitis B type virus were determined through above method as 62 nm and 44 nm, respectively.

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Two-dimensional granulized J-aggregated domains of amphiphilic spiropyran molecules in a Langmuir-Blodgett film system could be visualized electron microscopically. A study by a technique of ESR suggested that the formation of J-aggregates might be accompanied with the appearance of a new ESR signal.

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