Multi-layered nanoball as high performance permselective membrane

Multi-layered structure of the core-polymerized polymeric micelle carrying aldehyde groups (aldehyde-nanoball) and polyallylamine (PAA) was prepared on a porous polymer membrane by the layer-by-layer (LBL) coating, followed by reductive amination. Aldehyde-nanoball with diameter of 40 nm was made from a core-shell type polymeric micelle of acetal-poly(ethylene glycol)/polylactide-methacryloyl block copolymer (acetal-PEG/PLA-methacryloyl) by a gentle acid treatment to convert acetal into aldehyde group, followed by the polymerization of the methacryloyl group in the core. Permselectivity of hydrophilic macromolecules (dextran, myoglobin, albumin) through the nanoball-coated membrane was evaluated by the use of two-chamber cell. With an increasing number of the coating layers, permeation of the macromolecules was reduced in the molecular weight-dependent manner. Especially, in the case of protein molecules as solutes, a definite cut-off molecular weight was justified by changing the number of the coating layer. The multi-layered coating of nanoballs developed here is expected to be useful as a high performance separation membrane for proteinous compounds.