LAUSR

A series of charge-modified polyacrylonitrile (PAN) membranes with different surface charge properties and densities have been obtained via first grafting with hyperbranched polyethylenimine (PEI) and then ring-opening with 1,4-butane sultone. The obtained PAN-gr-PEI membranes and PAN-gr-PEIS membranes have hyperbranched polycation and hyperbranched zwitterions tethered on the surface, respectively. They were characterized in detail by FT-IR, AFM, XPS, SEM, WCA, and zeta-potential measurements. Bovine serum albumin (BSA) and lysozyme (Lys) were chosen as model proteins in order to evaluate the separation performance of the modified membranes via dead-end ultrafiltration. The membranes grafted with PEI of different densities have different surface chemical compositions but very similar surface charge properties. PAN and PAN-gr-PEI membranes are highly negatively charged and moderately positively charged. PAN-gr-PEIS membranes show typical amphoteric characteristics. The UF performance is highly dependent o...