Permanent surface modification by electron-beam-induced grafting of hydrophilic polymers to PVDF membranes

Abstract

Electron-beam-induced grafting of hydrophilic polymers was applied to modify PVDF membranes for biomedical applications. Grafting was performed by immersing the membrane in an aqueous solution of different hydrophilic polymers followed by electron-beam irradiation. The two polymer types are able to cross-link by recombination of adjacent radicals formed via the irradiation. Although the untreated membrane was already quite hydrophilic, the modification resulted in even lower water contact angles at the membrane surface indicating improved water wettability. The presence of different functional groups originating from the hydrophilic polymers was detected on the membrane surface by electrokinetic measurements. SEM investigations as well as porosimetry experiments showed that the grafted hydrophilic polymer layer is very thin; therefore, the membrane pore structure is not negatively affected. Soxhlet extraction revealed the stability of the modification for selected polymers: surface contact angles were comparable after extraction, and total organic carbon investigation of the extraction water revealed no significant loss of organic material. Investigated mechanical properties confirmed an increased stability due to cross-linking of the polymers. Undesired hemolysis was not detected with hemocompatibility tests, and coagulation was decreased with selected hydrophilic polymers. Because of the absence of any toxic material during surface modification and the high stability of the product, this method is believed to be suitable for the modification of membranes for medical applications, e.g. for improving the hemo-or biocompatibility.

Biocatalytic Self-Cleaning Polymer Membranes

“…However, the changes are not significant, and we can assume that the membrane structure was not destroyed or altered by the EB treatment nor blocked by the immobilized enzyme. Further investigation on the impact of EB on the membrane material was published before and confirms these results [22,24,25]. Table 3.…”

“…This way, links between the polymer matrix and the enzyme can be formed that are assumed to be side-unspecific. Previous work demonstrated the formation of covalent chemical bonds between the membrane polymer and the immobilized molecules by XPS analysis, which was supported by extensive extraction experiments [22][23][24]26,47]. It is worth emphasizing that the use of an aqueous system is a crucial requirement since different results were obtained in the dry state as also reported in the literature [48].…”

“…The EB treatment results in the generation of a mixture of ions, excited m described for the radiolysis of water [45] ensuring the activation of both the dis well as of the membranes [22][23][24][27][28][29]47]. The formed radicals/activated s reactions, such as cross-linking or recombination reactions.…”

“…This technology enables direct immobilization of functional organic molecules [22,23], engineering polymers [24], or even biomolecules [25,26] on a membrane's surface. The use of low-energy EB radiation combines surface activation (formation of activated species) of the membrane polymer and simultaneous covalent immobilization of the desired compounds from an aqueous system.…”

Tailoring Membrane Surface Charges: A Novel Study on Electrostatic Interactions during Membrane Fouling

“…For grafting modification the membranes were dipped into an aqueous solution of PEG (0.5 wt %) [48] or PSS (2 wt %) [48], followed by EB irradiation in wet state. Irradiation was performed in a N 2 atmosphere with O 2 quantities <10 ppm using a custom-made electron accelerator and an irradiation dose of 200 kGy.…”