To learn the impact of aqueous environmental species on the property of the isolated core of a water-soluble unimolecular micelle (UIM), a guest dye of erythrosine B (EB) is used as a probe to map the dynamic microenvironment of the UIM. PEGylation of branched polyethylenimine (PEI) with oxirane-functionalized polyethylene glycol (PEG) leads to a UIM of PEI@PEG, and the core is further chemically engineered. The resulting UIMs can irreversibly encapsulate EB exclusively by the core. It is found that the stacking of EB molecules is dependent on the electronic microenvironment of the UIMs, where a polar and ionic core favors a twist stacking of EB, but a less polar core results in an unprecedented parallel stacking of EB. Spectral analysis shows that EB is encapsulated along with its counter ion of Na+, and an exterior ion can cause dehydration of the UIMs but can hardly enter the UIMs; moreover, ion exchange through the PEG shell is actually allowed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 566–573

Charge-selective separation and recovery of organic ionic dyes by polymeric micelles (PMs) are reported. Branched polyethylenimine (PEI) functionalized with 4-cetyloxybenzaldehyde (CBA) via Schiff-base bonds (PEI@CBA) can extract an anionic dye from cationic contaminants, and transfer it from an aqueous phase into an apolar oil phase, and thus leading to separation. While a physical micelle of PAA@PS, with polyacrylic acid (PAA) as core and polystyrene (PS) as shell, can selectively extract a cationic dye from anionic contaminants. When polar, yet nonionic groups are eliminated from the core of a PM, charge selectivity can be significantly enhanced. Although many anionic–cationic dyes can form a poorly water-soluble complex or precipitate, separation is still feasible with a reasonably designed PM. Finally, entrapment of a guest by a PM is found easy but release may be difficult; in this case, PEI@CBA with an acid-sheddable shell, can recover the entrapped guest. It is also found the encapsulation of a dye is usually accompanied with dye stacking, resulting in a changed UV/vis spectrum. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 872–881

Topology-selective encapsulation of a guest is generally exclusively achieved by a well-defined host. In this article, a macromolecular reverse micelle (PEI@PS), with a hyperbranched polyethylenimine (PEI) as core and polystyrenes (PSs) as shell, is prepared and shown with excellent encapsulation and separation abilities. It is found that the encapsulation and phase transfer is kinetically dependent on the size of the dyes, creating a time window for the separation of dyes. All the experimental results show that the thickness and density of shell plays the most important roles in guest selectivity. In addition, highly size-selective release is also found. This macromolecular reverse micelle (PEI@PS) can find useful applications in the liquid–liquid or solid–liquid extraction separation, especially for the latter.© 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1273–1281

Polymeric micelles showing charge selective and pH-reversible encapsulation are reported. It is found that for a guest mixture of organic cationic–anionic 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 anionic–cationic 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. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The separation of structurally similar molecules remains a general challenge; here, we report that a roughly defined macromolecular nanocapsule can efficiently separate a variety of structurally similar mixtures. The nanocapsule is a core−shell amphiphilic macromolecule (CAM) hydrophobically derived from hyperbranched polyethylenimine with 2-hexadecyloxymethyloxirane. It is found that with further chemical core engineering of the CAM, its guest selectivity can be radically enhanced, although specific host−guest interaction is absent or ignorable in the system. As a result, two groups of structurally similar guests such as fluorescein/tetrachlorofluorescein, and rose bengal/erythrosine B/eosin Y, can be well recognized by the CAMs. It is known that a complex (fuzzy) system is generally characterized by complexity and nonlinearity; thus core engineering of a CAM is possible to amplify the difference of the competitive guests and lead to effective guest differentiation, such a mechanism is called supramolecular fuzzy recognition (SFR). Our results demonstrate that with appropriate combination of various elementary interaction styles, SFR can lead to effective recognition of a wide spectrum of mixtures. Moreover, a SFR host can be roughly defined in structure and thus readily available. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The synthesis and properties of a macromolecular nanocapsule derived from hyperbranched polyethylenimine (HPEI) with well-defined hybrid shell of poly(ethylene oxide) monomethyl ether (mPEO) and polystyrene (PS) are described. HPEI is treated in sequence with 4-glycidol-2,2,6,6-tetrametyl-piperidin-1-oxyl, succinic anhydride, mPEO, leading to a HPEI derivative compatible with nitroxide-mediated living radical polymerization of styrene, thus a macromolecular nanocapsule, HPEI@PEO/PS, is available with a well-defined and tunable hybrid shell of PEO and PS. Within certain PEO/PS ratio, the nanocapsule is soluble in a number of organic solvents as well as in water. The nanocapsule exists as three layer onion-like particle (HPEI@PS@PEO) in water, whereas in chloroform it exists as a hybrid shell particle (HPEI@PEO/PS), and the particles generally exist in the form of unimolecular micelle. In a biphasic water/chloroform mixture, the nanocapsule can transfer anionic, water-soluble guest from an aqueous phase to the chloroform phase; while when dissolved in water, the nanocapsule can efficiently capture both ionic and apolar solutes. Release of the guest can occur under the stimulus of pH or the switch of medium. This is the first example of a unimolecular micelle that can simultaneously deliver both polar and apolar guests. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 681–691, 2010