High cut-off membrane: evaluation of pore collapse and the synergistic effect of low and high molecular weight polyvinylpyrrolidone

High cut-off (HCO) membranes are the new class of membranes using in several applications like blood purification systems. In the current study, efforts were based upon achieving the HCO membrane with defined properties. Membrane pore collapse is the most challenging problem recognized as an undesirable phenomenon occurring in the drying stage of membrane preparation. Herein, this phenomenon was investigated in detail. The results verified that further of liquid surface tension, other parameters including viscosity, boiling point, polarity, and solubility parameters can be effective on the formation or prevention of this phenomenon. After preventing the pore collapse phenomenon, the simultaneous effect of low and high molecular weights polyvinylpyrrolidone (PVP) to achieve the HCO membrane was evaluated. PVP-K90 is used as a hydrophilizing agent and PVP-K17 is a low molecular weight polymer utilized as a pore-former additive. The synergistic effects of both grades of PVP, provide appropriate membrane features. Contact angle analysis indicated that by incorporation of PVP-K90 in casting solution, membrane hydrophilicity was increased tangibly. With the addition of more content of PVP-K90 higher than 3 wt%, pure water permeability (PWP) of the membrane was decreased. With adding PVP-K17 till 5 wt%, membrane PWP was enhanced significantly which confirmed the pore-former property of this additive. Moreover, mean pore diameter of membranes was increased and subsequently MWCO was enhanced to a higher value with the addition of this pore-former additive. MTT analysis endorsed the biocompatibility of membranes.

Automated summary

Efforts in this study focused on achieving HCO membranes with defined properties, facing challenges such as membrane pore collapse. By investigating various parameters and utilizing both high and low molecular weight polyvinylpyrrolidone (PVP), researchers successfully improved membrane features and pore structure. Contact angle analysis showed increased membrane hydrophilicity with PVP-K90 and enhanced pure water permeability with PVP-K17, leading to improved membrane performance and biocompatibility as confirmed by MTT analysis.