Preparation of ethylene vinylalcohol copolymer membranes suitable for ligand coupling in affinity separation

Hydrophilic microfiltration membranes with functional groups that can be used as coupling sites for ligands are of central interest in affinity separation, especially in view of biomedical applications. In this study, we employed ethylene vinyl alcohol copolymer (EVAL) to prepare macrovoid-free open cellular-type membranes with a high internal surface area and interconnectivity that can chemically be modified in aqueous and organic media. To tailor the required membrane morphology, we investigated the ternary water/DMSO/EVAL system and quaternary systems using a series of n-alcohols (n=2¿12) as non-solvent additives in the casting solution. Addition of solvent (DMSO) to the coagulation bath (water) performed in the ternary system to delay the onset of liquid¿liquid demixing, resulted in structures dominated by solid¿liquid demixing before macrovoid formation was completely suppressed. The symmetric particulate membranes obtained did not display the necessary mechanical strength. Addition of medium chain alcohols (n=7¿8) in the casting solution yielded macrovoid-free cellular membranes with a significantly higher pore interconnectivity and structural integrity upon drying. A model is proposed to understand the influence of the alcohol chain length and concentration on the membrane morphology.