Lipeng He

Star-like supramolecular polymers fabricated by a Keplerate cluster with cationic terminated polymers and their self-assembly into vesicles

The electrostatic combination of a Keplerate cluster, [Mo(132)O(372)(CH(3)COO)(30)(H(2)O)(72)](42-) with cationic terminated poly(styrene) yields polyoxometalate-based supramolecular star polymers, which can further self-assemble into vesicular aggregates in CHCl(3)-MeOH mixed solvent.

Synthesis and characterization of a luminescence metallosupramolecular hyperbranched polymer

A luminescence supramolecular hyperbranched polymer is reversibly fabricated by successively adding acid and base to a solution of an AB2 platinum(II) monomer in dichloromethane on the basis of acid-base controllable host-guest recognition of dibenzo[24]crown-8 moieties with dialkylammonium ion centers.

Spherical polymer brushes in solvents of variable quality: an experimental insight by TEM imaging.

The spherical micelle and vesicle composed of [PW12O40](3-) and poly(styrene-b-4-vinylpyridinium methyl iodide) are regarded as a model system to study spherical polymer brushes (SPBs) in solvents of various quality. The pure repulsions occur for the brush chains in the chloroform solution and chloroform/methanol mixture with a methanol volume ratio of 9.1%, where the grafted polystyrene chains have a relatively extended conformation. Further increase in the methanol concentrations leads to the presence of the intra/inter-brush van der Waals attractions. Transmission electron microscopy studies show that there is a coexistence of isolated and oligomeric SPBs and multi-SPB aggregates (MSAs) with the methanol content from 17% to 23%. Only MSAs are detected with the increasing methanol content. Both the corona and core shrink significantly in the isolated and oligomeric SPBs and MSAs. The full interpenetration of the grafted chains is observed between the cores in the oligomeric SPBs and MSAs.

Supramolecular polymerization induced self-assembly into micelle and vesicle via acid–base controlled formation of fluorescence responsive supramolecular hyperbranched polymers

Two asymmetric conjugated monomers of AB2-1 and AB2-2 with both dibenzo-24-crown-8 and dibenzylamine groups can self-assemble to form micellar and vesicular aggregates under acidic conditions, during which supramolecular hyperbranched polymers form controllably via host–guest recognition between dibenzo-24-crown-8 and dibenzylammonium groups.

Acid–base-controlled and dibenzylammonium-assisted aggregation induced emission enhancement of poly(tetraphenylethene) with an impressive blue shift

Three conjugated poly(tetraphenylethene)s grafted with dibenzo-24-crown-8 (DB24C8) groups, P-O, P-M and P-P, have been synthesized via Suzuki cross-coupling polymerization, in which the tetraphenylethene (TPE) units are connected at the ortho, meta and para positions, respectively. These conjugated polymers inherit the aggregation-induced emission feature of the TPE unit and thus their emission intensities increased significantly in the THF–water mixture solvents. The enhanced emission intensities highly depend on the connection modes of the TPE units and are in the order of P-O < P-M < P-P. Furthermore, the aggregation-induced emission enhancement (AIEE) feature can be activated by the acid–base-controlled complexation of DB24C8 groups with a dibenzylammonium chloride based molecule, protonated C12-2. The reduplicative complexation induces step-by-step emission enhancements together with morphological transitions from micellar to vesicular in the systems of P-O/C12-2 and P-M/C12-2. In the case of P-P/C12-2, of note is that the complexation not only leads to an AIEE feature but also a significant blue shift of the emission band from 515 to 483 nm. Both of these are really reversible under the acid–base-controlled condition. These polymer materials are of great importance for their potential application in the fields of optoelectronic devices and chemical and biomedical sensors.

Fusogenic Metallosupramolecular Brush Vesicles

The electrostatic combination of a cationic metallosupramolecular polyelectrolyte (Fe-MSP) with sulfonate-terminated polymers leads to the formation of metallosupramolecular brushes (MSBs). The resulting MSBs can self-assemble into vesicular structures in chloroform/methanol (v/v = 1:1) mixture solvents. The rigid-rod Fe-MSP chain has to bend for the formation of the vesicles, which accompanies the presence of a lateral tension and thus induces a spontaneous vesicle fusion with an hour-scale fusion time. For this much longer fusion process, the arrow-like protrusion, stalk-like intermediate, and hemifusion diaphragm are clearly observed by transmission electron microscopy. The complete fusion into larger vesicles significantly releases the lateral tension.

Multiple stimuli-responsive supramolecular gels constructed from metal–organic cycles

Two supramolecular networks are constructed from a crown ether based metal–organic cycle and dibenzylammonium based poly(e-caprolactone)s through multiple host–guest interactions. One of the networks can form organogels at higher concentrations, which show multiple stimuli-responsive behaviors under external stimuli, such as temperature, pH and ions.

Morphology-dependent AEE performance of conjugated poly(tetraphenylethene)s

The relationship between aggregation-enhanced emission (AEE) features and aggregation morphologies of AEE-active conjugated polymers in solvents of weakened quality is of fundamental importance to their optoelectronic, sensing or imaging applications. To address this correlation, we synthesized three conjugated poly(tetraphenylethene)s, o-PTPE, m-PTPE and p-PTPE, via Sonogashira cross-coupling polymerization. Among them, the 1,2-bis(4-ethynylphenyl)-1,2-diphenylethene (TPEE) units are linked at the ortho, meta and para positions of the phenyl groups, respectively. They show typical AEE behaviors in solvents of weakened quality, but with different spectral trends in different solvent mixtures. Concomitantly, these conjugated polymers self-assemble to form free-standing sheets with a thickness of ca. 10 nm and a micrometric plane in the toluene/methanol mixture solvents with moderate methanol contents. Solid nanospheres form when the solvent quality was further weakened with the increasing methanol content. o-PTPE and p-PTPE self-assemble into hollow nanostructures in chloroform/hexane mixtures. These aggregates are typically mesostable and dynamic in solution and can be further transformed into solid nanospheres. However, in the chloroform/methanol solvents, the conjugated poly(tetraphenylethene)s form solid nanospheres. These aggregation morphologies and evolutions can be directly correlated to the AEE spectral behaviors. In the solvents of weakened quality, o-PTPE, m-PTPE and p-PTPE, which are completely hydrophobic semiflexible homopolymers, can be packed into ordered nanostructures such as nanospheres, hollow nanoassemblies and free-standing sheets. This self-assembly mode has transcended the classical amphiphilicity paradigm of micelle-like nano-objects fabricated by amphiphilic (macro)molecules in selective solvents.

E/Z isomerization effects on aggregation-enhanced emission of tetraphenylethene derivatives assisted by host–guest recognition

Pure stereoisomers of tetraphenylethene derivatives functionalized with dibenzylamine groups, E and Z conformers, were successfully synthesized. Their aggregation-enhanced emissions, which occurred through host–guest recognition with a dibenzo-24-crown-8 based tetraphenylethene under an acid condition, showed recognizable isomerization effects.