Cyclodextrins （CDs） are regarded as one kind of the most important and promising macrocyclic oligosaccha- rides, which contain hydrophobic internal cavities capable of hosting various guest molecules. CDs are water-solu- ble, non-toxic, commercially available as well as low-cost. Because of these favorable characteristics, cyclodextrin chemistry has created a great number of interesting works covering different fields, in particular CD-based porous nanocapsules （CDPNCs）. Chemical cross-linking is an important way developed to prepare CDPNCs. CDPNCs can be obtained using different cross-linkers and preparation methods, such as homogeneous method, miniemulsion po- lymerization, and emulsion-solvent evaporation method. Because of cross-linking, a three-dimensional network is built which forms the porous structure in CDPNCs with the cavities of CDs. Attributed to the porous structure, CDPNCs exhibit excellent performances in encapsulation of targeted molecules and realization of controllable re- lease, indicating a promising prospect in applications such as drug delivery systems and environment protection.
Amphiphilic cyclodextrin-calixarene conjugates 1 and 2 were synthesized from "click chemistry", and their self-assembly behaviors were investigated by transmission electron microscopy, and atomic force microscopy. The results obtained show that 1 and 2 can self-assemble to form distinctly different aggregations, and the morphology of aggregations critically relies on the polarity and hydrophilicity of the solvent.
Aggregation of 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin (TPPS) was investigated in complex micelles composed of poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP) and poly(2-(dimethylamino)ethyl methylacrylate)-b-poly(Nisopropylacrylamide) (PDMAEMA-b-PNIPAM) in aqueous solutions.The resultant complex micelles had a complex P4VP/ PDMAEMA/TPPS core and a mixed PEG/PNIPAM shell.Different noncovalent interaction modes between the porphyrin and each copolymer accomplished a co-effect on the aggregation of TPPS.The formation of aggregates was pH-dependent.At pH 3.2–6.5,TPPS existed as a mixture of H-aggregates and monomers because of the aromatic-aromatic interaction with P4VP and electrostatic interaction with PDMAEMA.The monomers translated into J-aggregates,stabilized by electrostatic interaction with the both polyelectrolyte blocks,upon decreasing the pH to 1.6.The free-base monomer was the one and only form for the dye at pH 11.0 due to aromatic stacking with the pyridyl rings.
A twin-axial hetero[5]pseudorotaxane was constructed based on 1-hexyl-4,40-bipyridinium guest 1 and cucurbit[8]uril（CB[8]）and a-cyclodextrin（a-CD）.In its structure,CB[8]included two bipyridinium units to realize the twin-axial mode,and the hexyl chain was threaded into the cavity of a-CD.The[5]pseudorotaxane contains two types of macrocyclic hosts while the single axial and twin axial modes co-exist in its structure.The transformation of[5]pseudorotaxane could be realized by the addition of acid and 2,6-dihydroxynaphthalene（HN）.
Li-Hua WangZhi-Jun ZhangHeng-Yi ZhangHai-Lang WuYu Liu
A [3]rotaxane I involving two naphtho-21-crown-7 （N21 C7） rings and a dumbbell-shaped component 4 was synthesized. The dumbbell-shape molecule 4 contains one viologen nucleus, two secondary alkyl ammonium sites and two phenyl stoppers. After threading the N21C7 ring with the thread-like ammonium guest 3, the copper（l）-catalyzed Huisgen alkyne-azide 1,3-dipolar cycloaddition （CuAAC ＂click＂ reaction）, was performed to connect the pseudorotaxanes with viologen unit 2 and generate 1. Through treating the [3]rotaxane by the base and acid circularly, the two N21 C7 rings can make shuttling motion along the axle. Meanwhile the distance between the electron-deficient viologen unit and the electron-rich naphthol group can be adjusted precisely along with a remarkable intramolecular charge- transfer （CT） behavior.
