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The selection of a polymer for use as a gas separation membrane material is essentially based on a number of intrinsic properties that control the performance characteristics of the separation system. Primarily, these properties are gas permeation properties, mechanical behavior and cost. Unfortunately, most polymers that are highly permeable are usually not very selective. On the other hand highly selective polymers are not very permeable. This typical trade-off has been well demonstrated by Robeson1 who has analyzed in great detail the existing permeability data for a large number of polymers. It has been noted by few authors,2 that polymer molecular structure can be manipulated to achieve the most favorable balance of transport properties. Resting and Fritzsche3 have made note of the importance of the effect of molecular weight (MW) of polymers on the performance of gas separation membranes. According to these authors, when dense membranes are prepared from equal viscosity sols, porosity and free volume (Vf) will increase with polymer molecular weight. They have also pointed out extremely favorable mechanical properties, along with high permeability characteristics of membranes from higher molecular weight polymers.

Since Willem Kolff, Nils Alwall and other pioneers performed the first regular dialysis treatments on uremic patients in the 1940s, dialysis membranes have been under continual development with respect to improved functionality and biocompatibility. Bulky ‘plate kidneys’ which were used in the early days of clinical hemodialysis have nowadays been replaced by highly optimized disposable membrane devices containing state of the art synthetic hollow fiber membranes in combination with sophisticated volume-balancing dialysis machines.

Bioreactors are widely used in biotechnology for numerous applications. Typically such bioreactors are used with isolated enzymes, enzyme-complexes, whole cells or even only cell extracts without defined composition. The immobilisation of these producing systems may be done by different techniques. Beneath the physical or chemical bonding to non soluble matrices the compartimentation of the reactors with semipermeable membranes becomes more and more important. The membranes are similar to those, which are used in ultra filtration and dialysis techniques.

Immobilized biocatalysts have widespread applications in areas like organic synthesis, pollution control and for diagnostic purposes. Enzymes can be immobilized on different supports like polymeric beads, gels, and membranes. Immobilization eliminates the need to separate an enzyme from the product solution and allows these expensive compounds to be reused. In addition, the thermal stability, pH stability, and storage stability of an enzyme may be increased as a result of immobilization.

Loeb and Sourirajan invented the first integrally-skinned membrane in 1960 for desalination by phase inversion of cellulose acetate sols (1). In the integrally-skinned membrane, the skin and substructure are composed of the same material. The skin layer determines both the permeability and selectivity of the bilayer, whereas the porous substructure functions primarily as a physical support for the skin. Differences in structure between the two layers are the result of interfacial forces and the fact that solvent loss occurs more rapidly from the air-solution and solution-nonsolvent interfaces than from the solution interior (2).

Sheet1) and hollow fiber membranes with stabilized porous structure were formed from poly(methyl methacrylate) (PMMA) by making use of stereocomplex phenomenon, which occures in the mixture solution of isotactic and syndiotactic PMMA, and which is a stoichiometric and thermoreversible sol-gel phase transition phenomenon.2)–5) This report will show the formation processes, permeability characteristics, and medical applications of PMMA membranes.

The operational aspects of automated hollow fiber ultrafiltration systems are reviewed both with respect to filtrate utilization as well as a recovery system for membrane-retained species. Typifying the former is the removal of pyrogens, while an example of the latter is the removal and subsequent recovery of f2 bacteriophage from both tap and lake water. While preparation of colloid-free filtrate can be easily explained by sieving governed by the pore size of the membrane, the recovery of retained species necessitates a more complex model. With respect to phage, logarithmically decreasing concentrations of phage are recovered in the concentrate solution by successive backflushes of the membrane with filtrate. A model is proposed to explain the logarithmic decrease in concentration as a function of the backflush flux and volumetric throughput. The model can be used to predict the total number of original phage in a water sample filtered through the unit on the basis of an assay of the phage in a single backflush. Phage was selected as a model system to establish operational parameters for extending these studies to encompass enteroviruses in water.

The characteristics of the structure and the properties of polymethyl methacrylate (PMMA) hollow fiber are its uniformity of structure, hydrophobic property and wider performance compared with cellulosic membranes[1,2]. For these characteristics its structural analysis will be simplified.

Loeb and Sourirajan invented the first integrally-skinned membrane in 1960 for desalination by phase inversion of cellulose acetate sols (1). In the integrally-skinned membrane, the skin and substructure are composed of the same material. The skin layer determines both the permeability and selectivity of the bilayer, whereas the porous substructure functions primarily as a physical support for the skin. Differences in density between the two layers are the result of interfacial forces and the fact that solvent loss occurs more rapidly from the air-solution and solution-nonsolvent bath interfaces than from the solution interior (2).

A realistic model for the diffusional type of an asymmetric hollow fiber enzyme reactor with non-linear reaction kinetics is presented. An efficient collocation method was used for the steady-state solution resulting in a substantial decrease of the computing time. The results are presented in a concise graphical form.

Cells of Hansenula henriici possessing specific activity (in the 0.0017–0.065 U/mg/min. range) towards cellobiose, have been immobilized into Amicon hollow-fiber modules, used as ultrafiltration devices. The performance of the resulting membrane enzyme reactor (REM) was tested with cellobiose solutions (0.25–1% in buffer at pH=4,4) as substrate. More than 98% of the cells resulted immobilized in the module and a good retention of hydrolytic activity was observed.