Charge selective encapsulation by polymeric micelles with cationic, anionic, or zwitterionic cores

Polymeric micelles showing charge selective and pH-reversible encapsulation are reported. It is found that for a guest mixture of organic cationicanionic dyes, a unimolecular micelle (PEI@PS) with a polystyrene (PS) as shell and a hyperbranched polyethylenimine (PEI) as core can exclusively entrap the anionic one; and a physical micelle consisting of brush-like macromolecule (mPS-PAA) with multi PS-b-polyacrylic acid (PAA) as grafts can exclusively entrap the cationic one. A covalent micelle (PEI-COOH@PS) bearing a zwitterionic core, that is, PEI covalently derived with dense carboxylic acids, can undergo highly pH-switchable charge selective and pH-reversible encapsulation. Both PEI@PS and mPS-PAA can be used for highly charge-selective separation of ionic dyes but the pH-reversibility of the encapsulation is relatively limited. In contrast, PEI-COOH@PS is less effective to differentiate the anioniccationic dyes but is well recyclable. A physical micelle obtained from the self-assembly of PEI and mPS-PAA shows similar property to PEI-COOH@PS. The combination of these micelles in mixture separation can enhance the recyclability of the micelle and widen the spectrum of mixtures that can be well separated. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012