Asymmetric Isoporous Membranes of 2-Vinylpyridine-Styrene Linear Diblock Copolymers: Fabrication and Evaluation in Water Treatment

Herein, we report the synthesis via controlled reversible addition-fragmentation chain transfer (RAFT) polymerization of amphiphilic 2-vinylpyridine-<i>b</i>-styrene (2VPy-<i>b</i>-Sty) diblock copolymers of high molar masses (range: 52,100-304,000 g mol^-1) and various compositions (range: 2VP content 11.6-59.2 mol%) and their use for the fabrication of nanoporous membranes. The successful synthesis of the amphiphilic diblock copolymers was confirmed through the characterization of their molar masses, molar mass distribution, and composition using GPC and ¹H-NMR spectroscopy, respectively. Subsequently, membranes of the diblock copolymers were fabricated following the "phase inversion" technique. The resulting membranes were characterized via scanning electron microscopy which revealed the presence of sphere percolation networks morphology for all diblock copolymers with <i>M_n</i> ranging from 120 to 300 kDa and 2VPy content between 10 and 15 mol% at the optimal conditions. Afterward, the developed membranes were evaluated in terms of their permeability towards water and in terms of their ability to retain two different microorganisms, namely, <i>Enterococcus faecalis</i> and <i>Escherichia coli</i>, that are known to be harmful to human health. The experimental water flux for a membrane with pore size around 60 nm was equal to 31,400 L h^-1 m² and expectedly decreased with the decrease in membrane pore diameter. The retention ability of membranes for <i>Enterococcus faecalis</i> and <i>Escherichia coli</i> was higher than 90%. In particular, the retention ability for <i>Enterococcus faecalis</i> was equal to 98.9% and for <i>Escherichia coli</i> was 91.4%. The toxicity of the produced membrane was also determined, and the measured value was relatively low, at 17%.