环糊精包合作用组装大分子网络

利用环糊精的包合作用可以组装构筑大分子网络体系.这种独特的组装方法交联模式简单、交联度易于调控,得到的网络体系既能为聚合物的缔合理论提供理想的实验模型,又能广泛用于黏度调节和药物控释.环糊精的独特结构及对多种客体分子的包合作用使其近年来成为分子组装研究的热点.本文综述了以环糊精包合作用构筑大分子网络的研究进展,分别介绍了链状大分子组装交联和环糊精分子管道结晶缔合这两种方法.     

Cucurbit[n]urils-related Multitopic Supramolecular Components: Design,Properties, and Perspectives

Cucurbit[n]urils (CBns) are an intriguing family of macrocyclic hosts whose chemistry has undergone rapid developments in recent decades. The initial interest in the synthesis, modifications and binding properties has shifted to areas focused on applications in drug storage, delivery, and release, external-stimuli responsive devices, and molecular nano-reactors. Since CBns are fruitfully complemented by cyclodextrins (CDs) in such systems, guest molecules that contain several binding sites are needed. These multitopic guests provide not only a scaffold for holding CBns and CDs together in appropriate arrangements but also allow for manipulation with supramolecular aggregates, e. g., reorganization or release of macrocycles. In this review, we summarize recent studies related to the design of multitopic guests. Binding motifs properties, the role of attractive or repulsive lateral interactions, the competition-compensation effect, and rotaxane versus pseudorotaxane manner are discussed.     

Novel supramolecular system of amphiphilic hyperbranched polymer with β-cyclodextrin and hyperbranched topography cavities: Synthesis and selective encapsulation

Novel supramolecular system of amphiphilic hyperbranched polymer with hyperbranched poly(β-cyclodextrin) core was designed and synthesized to accomplish a so-called selective encapsulation, where two types of guest molecules can be encapsulated into two types of molecular cavities from β-cyclodextrin (β-CD) and topography structure of hyperbranched polymer, respectively. The double molecular recognition behaviors from β-CD and hyperbranched cavities drive one guest to go into the former, the other guest to the latter. This selective encapsulation was further confirmed via the release profiles and sequences of Levofloxacin lactate (LL) and Phenolphthalein (PP). LL presents a sustained release period followed by an almost non-release stage, while PP releases on a quite slow rate at first, subsequently on the linearly increasing rate. At the early stage, the release of LL dominates in comparison with PP, and then the release rate of PP increases to play a determinate role in the release system. It can be attributed to the existence of two guests in the different molecular cavities with the different microenvironments. The observed selective encapsulation of supramolecular system is a new phenomenon, which is helpful to extend the application of CD-based hyperbranched polymers in supramolecular science and complex drug delivery system.     

pH‐/temperature‐sensitive supramolecular micelles based on cyclodextrin polyrotaxane

BACKGROUND: Based on the assembly strategy induced by host‐guest recognition in weak selective solvent, a kind of supramolecular nano‐micelles has been self‐organized from a water‐soluble diblock copolymer, poly(ethylene oxide)‐block‐poly(acrylic acid) (PEO‐b‐PAA), selectively included by ‐cyclodextrins (‐CDs). RESULTS: The spontaneous aggregation of rod‐like ‐CD/PEO‐based pseudo‐polyrotaxanes (pseudo‐PRs) drove the formation of square‐piece in aqueous media and thereafter evolved to spherical assemblies with or without hollow structure as time prolonged, which were stabilized by uncovered hydrophilic PAA segments. Such morphological evolvement attributed to hydrogen bonding between ··CCOOH in PAA and ··COH in ‐CD. However, when alkaline media was used to inhibit hydrogen bonding by ionizing ··CCOOH, the assemblies were only uniform spheres of ca. 100 nm. Meanwhile, the order stacking of PR rods became the basic building units all the time. Herein, the supramolecular PRs contributed to temperature‐response character, namely the formation of assemblies is reversible stimulated with temperature changes. Additionally, the inhibition of deceasing pH to the ionization of free PAA segments made assemblies fuse as microspheres. CONCLUSION: Such pH‐ and temperature‐sensitivity as well as the biocompatibility of components and water as media make a great potential of such nano‐particles as the biomedical materials with controlled‐release function. Copyright © 2007 Society of Chemical Industry     

Complex macromolecular architecture design via cyclodextrin host/guest complexes

The design of complex macromolecular architectures has driven macromolecular engineering over the past decades. The introduction of supramolecular chemistry into polymer chemistry provides novel opportunities for the generation of macromolecular architecture with specific functions. Cyclodextrins are attractive design elements as they form supramolecular inclusion complexes with hydrophobic guest molecules in aqueous solution affording the possibility to combine a large variety of building blocks to form novel macromolecular architectures. In the present critical review, the design of a broad range of macromolecular architectures driven by cyclodextrin host/guest chemistry is discussed, including supramolecular block copolymers, polymer brushes, star and branched polymers.     

环糊精包合客体分子机理的研究

环糊精具有独特的疏水空腔结构，与一些物质包合后．能显著改变这些物质的理化性能。本文在环糊精包合染料的基础上，探讨了环糊精包合客体分子的机理。认为包合物形成主要取决于环糊精和客体分子结构及两者作用力的大小。客体分子或其中某些基团的大小与环糊精空腔大小相近的易于包合，两者之间的作用力大小影响包合物的稳定性，疏水力是包合过程主要推动力。     

两亲性环糊精的合成研究进展

与天然环糊精相比,两亲性环糊精不仅包结客体分子,而且自组装形成囊状结构,是一类重要的药物载体.本文综述了两亲性环糊精的合成,并对其发展前景进行了展望.     

Supramolecular polymer gel with multi stimuli responsive,self-healing and erasable properties generated by host–guest interactions

A supramolecular polymer gel formed between triptycene-based bis(crown ether) and copolymer containing dibenzylammonium (DBA) moieties by host–guest interactions was described. We demonstrated the formation of the supramolecular polymer networks between the bis(crown ether) and the copolymer by the ¹H NMR spectroscopy and solution viscometry, and we also obtained a colorless and transparent supramolecular polymer gel at high concentration. Moreover, the supramolecular polymer gel showed multi-stimuli reversible responsiveness, such as thermo-, acid/base-, and chemo- induced gel–sol transitions. Furthermore, the result of rheological measurements showed the gel has an intrinsic self-healing property, and the thixotropic process could be repeated at least three times. Interestingly, when doped with spiropyran molecules, the supramolecular polymer gel could also be employed as erasable materials. Thus, these results could be highly anticipated to benefit for further construction of smart materials with high healing efficiency, and ultimately be used in practical application.     

环糊精介入与TiO_2光催化应用研究进展

环糊精特有的结构可以对疏水客体分子进行主-客体包合,它介入到TiO2光催化过程中,可以增加TiO2光催化材料对疏水客体的吸附,加快被包合客体底物分子的传质效率,增大化学反应动力学常数,提高TiO2的光催化降解活性。其对有机疏水底物分子的选择性识别包合作用,有望解决TiO2对高毒性不可生物降解污染物催化选择性低及催化活性不高的难题。根据近年来公开发表的国内外相关文献,对环糊精介入的TiO2光催化应用研究进行简要评述。     

Hydrogen bond‐mediated self‐assembly and supramolecular structures of diblock copolymer mixtures

This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self‐assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self‐assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry     

Thermodynamics of the encapsulation by cyclodextrins

Molecular encapsulation on a molecular basis can be performed by cyclodextrins. The inclusion of organic molecules into the interior changes the properties of these molecules, which may be used for a broad variety of applications. The affinity of guest molecules for the cavities of various cyclodextrins depends on the stereochemistry and on the interaction forces of the molecules involved. Calculations of the thermodynamic parameters show that the reaction entropy is highly important for the inclusion reaction. Completely different reaction mechanisms are observed for various types of cyclodextrins as some of these reactions show enthalpy–entropy compensation. Others are supported by the reaction entropy or are even entropically controlled. Protonation and deprotonation reactions contribute significantly to the inclusion reaction, as first of all the solubility of the compounds in water is strongly influenced by the acidity of the solution, and, moreover, all tautomeric forms of the compounds show different affinities to various cyclodextrins. Copyright © 2006 Society of Chemical Industry     

Synthesis and physicochemical characterization of amphiphilic block copolymer self‐aggregates formed by poly(ethylene glycol)‐block‐poly(ϵ‐caprolactone)

Diblock copolymers with different poly(ε‐caprolactone) (PCL) block lengths were synthesized by ring‐opening polymerization of ε‐caprolactone in the presence of monomethoxy poly(ethylene glycol) (mPEG‐OH, MW 2000) as initiator. The self‐aggregation behaviors and microscopic characteristics of the diblock copolymer self‐aggregates, prepared by the diafiltration method, were investigated by using ¹H NMR, dynamic light scattering (DLS), and fluorescence spectroscopy. The PEG–PCL block copolymers formed the self‐aggregate in an aqueous environment by intra‐ and/or intermolecular association between hydrophobic PCL chains. The critical aggregation concentrations of the block copolymer self‐aggregate became lower with increasing hydrophobic PCL block length. On the other hand, reverse trends of mean hydrodynamic diameters were measured by DLS owing to the increasing bulkiness of the hydrophobic chains and hydrophobic interaction between the PCL microdomains. The partition equilibrium constants (K_v) of pyrene, measured by fluorescence spectroscopy, revealed that the inner core hydrophobicity of the nanoparticles increased with increasing PCL chain length. The aggregation number of PCL chain per one hydrophobic microdomain, investigated by the fluorescence quenching method using cetylpyridinium chloride as a quencher, revealed that 4–20 block copolymer chains were needed to form a hydrophobic microdomain, depending on PCL block length. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3520–3527, 2006     

Fabrication of core or shell reversibly photo cross-linked micelles and nanogels from double responsive water-soluble block copolymers

Poly(butanedioic acid, 1-[3-[(2-methyl-1-oxo-2-propen-1-yl)oxy]propyl] ester)-b-poly(methoxydi(ethylene glycol) methacrylate-co-4-methyl-[7-(methacryloyl)oxyethyloxy] coumarin) (PSPMA-b-P(DEGMMA-co-CMA)) block copolymer was synthesized via atom transfer radical polymerization (ATRP). The temperature and pH responsive micellization behaviors of PSPMA-b-P(DEGMMA-co-CMA) were investigated to obtain P(DEGMMA-co-CMA)-core and PSPMA-core micelles. After the two types of micelles were exposed to 365 nm UV light, core cross-linked (CCL) micelles and shell cross-linked (SCL) micelles were facilely prepared. The photo cross-linking was proved to be reversibly controlled under alternative irradiation of 365 nm and 254 nm UV light. More interestingly, block copolymer nanogels were fabricated by translating the hydrophobic core of the CCL and SCL micelles into hydrophilic via adjusting the temperature and pH. The sizes of the block copolymer nanogels can be facilely controlled by UV light irradiation. The introduction of reversibly photo cross-linkable groups into the double responsive block copolymers provides a novel approach to develop more sophisticated, controllable, and smarter nanocarriers that might have great potentials in biomedical applications.     

Poly(ε-caprolactone) electrospun nanofibers containing curcumin nanocontainers: enhanced solubility,dissolution and physical stability of curcumin via formation of inclusion complex with cyclodextrins

Supramolecular nanocontainers of cyclodextrins (α- and β-CD)/curcumin (CUR) were prepared by inclusion complex (IC) forming between CDs and guest molecule at two conditions. Formation of the inclusion complex between CDs and CUR at various conditions in solid phase was characterized by various methods. Solubility and in vitro dissolution of obtaining CUR nanocapsules were investigated and results showed that encapsulation of CUR, improved CUR bioavailability with a controllable release. Electrospun nanofibers of poly-ε-caprolactone (PCL) containing CUR/CDs inclusion complex of various conditions have been fabricated using a conventional electrospinning process and indicated that these nanofibers are bead-free.     

Intelligent micellar polymeric nanocarriers for therapeutics and diagnosis

Polymeric micelles can be designed and synthesized to bear polymeric blocks with different hydrophilicities; this triggers their self‐assembly into micellar aggregates similar to those generated with traditional surfactants. The basic structure consists of a hydrophobic core, capable of containing guest substances, and a hydrophilic shell, which stabilizes the payload and protects it from external degradation or prevents its quick elimination from the body. The accumulation of block copolymer micelles (BCMs) in a target cell or tissue can be accomplished by two main mechanisms, passive and active targeting; this allows the payload release at the site of action when desired. Hence, in this general overview, we pay special attention to newly developed single‐stimulus‐ and multi‐stimuli‐responsive delivery systems capable of disassembling and reassembling (in some cases) as a response to changes in their physicochemical properties. Also, special interest is also devoted to multifunctional BCMs incorporating multiple therapeutic agents and/or multiple imaging contrast agents, which can be considered the new generation (third generation) of drug‐delivery systems, that is, nanotheranostic platforms. Finally, a summary of BCM‐based drug‐delivery systems currently under clinical trials is given. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42650.     

Thermoresponsive Interplay of Water Insoluble Poly(2-alkyl-2-oxazoline)s Composition and Supramolecular Host–Guest Interactions

A series of water insoluble poly[(2-ethyl-2-oxazoline)-ran-(2-nonyl-2-oxazoline)] amphiphilic copolymers was synthesized and their solubility properties in the presence of different supramolecular host molecules were investigated. The resulting polymer-cavitand assemblies exhibited a thermoresponsive behavior that could be modulated by variation of the copolymer composition and length. Interestingly, the large number of hydrophobic nonyl units across the polymer chain induced the formation of kinetically-trapped nanoparticles in solution. These nanoparticles further agglomerate into larger aggregates at a temperature that is dependent on the polymer composition and the cavitand type and concentration. The present research expands the understanding on the supramolecular interactions between water insoluble copolymers and supramolecular host molecules.     

Dual Stimuli-Responsive Cross-Linked AIE Supramolecular Polymer Constructed through Hierarchical Self-Assembly

Herein, we report the successful construction of a new family of dual stimuli-responsive AIE cross-linked supramolecular polymer through the strategy of hierarchical self-assembly. A novel dipyridyl donor building block G1 containing tetraphenylethylene (TPE) moiety was designed and synthesized. Notably, two nitrile units were attached onto G1 , which were employed as the guest for the further host-guest interaction with pillar[n]arene derivatives. The rhomboidal metallacycle G2 with four nitrile units was firstly constructed through coordination-driven self-assembly. Subsequently, the cross-linked supramolecular polymers H₂⊃G2 were then generated through host-guest interactions. It should be noted that the obtained supramolecular polymer displayed interesting AIE properties due to the restriction of TPE intramolecular motions within the polymeric network. More importantly, by taking advantages of dynamic nature of both coordination bonds and host-guest interactions, the resultant supramolecular polymer displayed dual stimuli-responsive fluorescent transitions under different stimuli such as the competitive guest and halide anion.     

Dual stimuli-responsive supramolecular polymeric nanoparticles based on poly(<Emphasis Type="Italic">α</Emphasis>-cyclodextrin) and acetal-modified <Emphasis Type="Italic">β</Emphasis>-cyclodextrin-azobenzene

To aim at pH environment in tumor tissue and light-controlled drug release, UV and pH dual-responsive supramolecular polymeric nanoparticles mediated by host-guest interactions of poly(α-cyclodextrin) and acetal-modified β-cyclodextrin-azobenzene were developed in this work. The host molecule was poly(α-cyclodextrin) and the guest molecule was composed of acetal-modified β-cyclodextrin with one azobenzene linked. The inclusion of α-cyclodextrin and azobenzene leaded to amphiphilic supramolecular polymer, which further self-assembled to form supramolecular polymeric nanoparticles in aqueous medium. UV and pH responsiveness of supramolecular polymeric nanoparticles attributed to azobenzene and acetal, respectively. Supramolecular polymeric nanoparticles based on poly(α-cyclodextrin) and acetal-modified β-cyclodextrin-azobenzene with the average diameter of sub-100 nm were controllable to release the drugs regulated by pH and UV.     

Construction of a Artificial Glutathione Peroxidase with Temperature‐Dependent Activity Based on a Supramolecular Graft Copolymer

A supramolecular artificial glutathione peroxidase (PNIPAM‐CD‐g‐Te) was prepared based on a supramolecular graft copolymer. PNIPAM‐CD‐g‐Te was constructed by supramolecular host–guest self‐assembly. Significantly, PNIPAM‐CD‐g‐Te displayed noticeable temperature‐dependent catalytic activity and typical saturation kinetics behavior. It was also proved that the change in the self‐assembled structure of PNIPAM‐CD‐g‐Te during the temperature‐dependent process played a significant role in the temperature‐dependent catalytic behavior. The construction of PNIPAM‐CD‐g‐Te based on supramolecular graft copolymer endows artificial GPx with temperature‐dependent catalytic ability, enriched catalytic centers, and homogeneously distributed catalytic centers. This work bodes well for the development of other biologically related host–guest supramolecular biomaterials.