Laboratory-made asymmetric polyurethane membranes designed for immunoisolation were investigated. Two types of EK and ES membranes were prepared in different spinning conditions.
The membrane structure was characterised by the skin pore radius measurements using differential scanning calorimetry (DSC). Diffusive transport properties of membranes were determined by in vitro method for albumin and creatinine. The scanning electron microscopy (SEM) was applied to study the morphology of membranes.
It has been found that the DSC technique is a useful tool for the evaluation of pore radii in the skin layer for PU membranes. Calculated pore radii were in the range from 1.95 to 2.47 nm for the EK and ES types. A correlation between the skin pore radii and the transport properties was not found in this case of investigated membranes. However, the transport properties data can serve for the estimation of selectivity of membranes. Thus, the selectivity of membranes for solutes of various molecular size was estimated from the D m/D w ratio of diffusion coefficients for albumin and creatinine. The SEM micrographs reveal the finger-like internal structure of capillary membranes, as well as various skin thickness.