Reversible Metallo‐Supramolecular Block Copolymer Micelles Containing a Soft Core

An amphiphilic metallo‐supramolecular poly(ethylene‐co‐butylene)‐block‐poly(ethylene oxide) diblock copolymer containing a bis(2,2′:6′,2″‐terpyridine)ruthenium(II) complex as a supramolecular connection between the two constituting blocks was used to prepare stable aqueous micelles. The micelles were characterized by dynamic light scattering and atomic force microscopy. Individual micelles were observed together with aggregates of micelles. Only the addition of a large excess of competitive ligand caused the cleavage of the very stable ruthenium complex.     

Core Cross-Linked Polymerized Micelles and Dendronized Nanoparticles

Polymerization of 11-acryloylaminoundecanoic acid and its copolymerization with diacrylic monomers were performed under different conditions in micellar (Na-salt in water) and non-micellar states. The effect of conditions of the syntheses on molecular mass of the polymers and hydrodynamic characteristics of their macromolecules was studied. Ionic complexes of core-cross-linked polymerized micelles with different dendrons bearing polymerizable peripheral groups were obtained and their trial polymerizations were performed.     

Formation of Vesicles and Micelles in Aqueous Systems of Tetrameric Acids as Determined by Dynamic Light Scattering

A comprehensive dynamic light scattering (DLS) study on the system BP10Na₄/water is presented. BP 10Na₄ is a tetrameric fatty acid in sodium form. In order to change molecular packing conditions both electrolyte (NaCl) and alcohol (1-butanol, 1-pentanol) are added to the surfactant system. Phase diagrams of the systems reveal not only an extensive micellization, but also the occurrence of a lamellar liquid crystalline D phase. The DLS study shows an existence of vesicles at very dilute BP10Na₄ concentrations ( ?cmc) and also a co-existence of micelles and vesicles at higher BP10Na₄ concentrations. Cryo-TEM pictures verify the existence of the vesicles. Based on the DLS and SLS experiments the weight-average molar mass of the micelles are estimated to be 13500 g/mol at 100 mM NaCl and 22700 g/mol at 600 mM. The corresponding aggregation numbers are 13 and 22, respectively.     

Hydrogels Composed of Organic Amphiphiles and α‐Cyclodextrin: Supramolecular Networks of Their Pseudorotaxanes in Aqueous Media

Mixtures of N‐alkyl pyridinium compounds [py‐N‐(CH₂)_nOC₆H₃‐3,5‐(OMe)₂]⁺(X^?) ( 1b Cl: n=10, X=Cl; 1c Br: n=12, X=Br) and α‐cyclodextrin (α‐CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol–gel transition temperature, which ranges from 7 to 67 °C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and ¹³C CP/MAS NMR measurements, powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1b Cl (or 1c Br) and α‐CD was composed of pseudorotaxanes with high crystallinity. ¹³C{¹H} and ¹H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1b Cl and α‐CD contains the corresponding [2]‐ and [3]pseudorotaxanes, [ 1b? (α‐CD)]Br and [ 1b? (α‐CD)₂]Br, while that from 1c Br and α‐CD consists mainly of [3]pseudorotaxane [ 1c? (α‐CD)₂]Br. 2D ROESY ¹H NMR measurements suggested intermolecular contact of 3,5‐dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between α‐CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C₆H₃‐1,3,5‐(OH)₃, and [py‐N‐nBu]⁺(Cl^?).     

生物相容性嵌段型聚电解质胶束在水溶液中的酶降解行为

采用激光光散射仪和原子力显微镜研究了生物相容性嵌段型聚电解质聚左旋乳酸-b-聚甲基丙烯酸二甲氨基乙酯(PLLA-b-PDMAEMA)胶束在水溶液中2个温度(室温25.0℃和人体温度36.8℃)和2个pH值(肿瘤pH=4.9和正常组织pH=7.4)条件下的酶降解行为. 酶降解过程中存在一个失活时间, 在此之前, 胶束的酶降解遵循逐个降解机理. 失活时间之后, 出现裂纹或是通道的胶束核为降低其在溶剂中的表面积, 从而降低体系自由能, 胶束之间发生了聚集. 升高温度后, 酶的活性提高, 初始降解速率加快. 由于pH=4.9时胶束壳层因静电斥力作用而较为伸展, 使得胶束降解更快.     

Effect of the Cationic Surfactant Moiety on the Structure of Water Entrapped in Two Catanionic Reverse Micelles Created from Ionic Liquid‐Like Surfactants

The behavior of water entrapped in reverse micelles (RMs) formed by two catanionic ionic liquid‐like surfactants, benzyl‐n‐hexadecyldimethylammonium 1,4‐bis‐2‐ethylhexylsulfosuccinate (AOT‐BHD) and cetyltrimethylammonium 1,4‐bis‐2‐ethylhexylsulfosuccinate (AOT‐CTA), was investigated by using dynamic (DLS) and static (SLS) light scattering, FTIR, and ¹H NMR spectroscopy techniques. To the best of our knowledge, this is the first report in which AOT‐CTA has been used to create RMs and encapsulate water. DLS and SLS results revealed the formation of RMs in benzene and the interaction of water with the RM interface. From FTIR and ¹H NMR spectroscopy data, a difference in the magnitude of the water–catanionic surfactant interaction at the interface is observed. For the AOT‐BHD RMs, a strong water–surfactant interaction can be invoked whereas for AOT‐CTA this interaction seems to be weaker. Consequently, more water molecules interact with the interface in AOT‐BHD RMs with a completely disrupted hydrogen‐bond network, than in AOT‐CTA RMs in which the water structure is partially preserved. We suggest that the benzyl group present in the BHD⁺ moiety in AOT‐BHD is responsible for the behavior of the catanionic interface in comparison with the interface created in AOT‐CTA. These results show that a simple change in the cationic component in the catanionic surfactant promotes remarkable changes in the RMs interface with interesting consequences, in particular when using the systems as nanoreactors.     

Binding and Sensing Properties of a Hybrid Naphthalimide–Pyrene Aza-Cyclophane towards Nucleotides in an Aqueous Solution

Selective recognition of nucleotides with synthetic receptors is an emerging direction to solve a series of nucleic acid-related challenges in biochemistry. Towards this goal, a new aza-cyclophane with two different dyes, naphthalimide and pyrene, connected through a triamine linker has been synthesized and studied for the ability to bind and detect nucleoside triphosphates in an aqueous solution. The receptor shows Foerster resonance energy transfer (FRET) in fluorescence spectra upon excitation in DMSO, which is diminished dramatically in the presence of water. According to binding studies, the receptor has a preference to bind ATP (adenosine triphosphate) and CTP (cytidine triphosphate) with a “turn-on” fluorescence response. Two separate emission bands of dyes allow one to detect nucleotides in a ratiometric manner in a broad concentration range of 10⁻⁵–10⁻³ M. Spectroscopic measurements and quantum chemical calculations suggest the formation of receptor–nucleotide complexes, which are stabilized by dispersion interactions between a nucleobase and dyes, while hydrogen bonding interactions of nucleobases with the amine linkers are responsible for selectivity.     

Ultrasonic Spectrometry of Aqueous Solutions of Alkyl Maltosides: Kinetics of Micelle Formation and Head‐Group Isomerization

At frequencies between 100 kHz and 400 MHz, ultrasonic attenuation spectra are measured at 25 °C for aqueous solutions of hexyl‐, heptyl‐, octyl‐, nonyl‐, and decyl‐β‐D ‐maltopyranoside as well as of decyl‐α‐D ‐maltopyranoside. The spectra with surfactant concentration c above the relevant critical micelle concentration (cmc) display three relaxation terms with discrete relaxation times. That with a relaxation time between 0.1 and 1.2 μs is due to exchange of monomers between micelles and the suspending phase. It is discussed in the light of the Teubner–Kahlweit–Aniansson–Wall model of the formation/decay kinetics of systems with Gaussian size distribution of micelles. The relaxation parameters are compared to those for solutions of other non‐ionic surfactants, such as alkyl monoglycosides and poly(ethylene glycol) monoalkyl ethers. At c<cmc this low‐frequency relaxation term is missing and at c≈cmc it is broadened, as is characteristic of solutions of oligomeric molecular structures rather than proper micelles. The relaxation terms with relaxation times between 6 and 15 ns and 0.7 and 2.3 ns reveal head‐group rotations around glycosidic angles and isomerization of the exocyclic hydroxymethyl group, respectively. These unimolecular reactions are also examined with a view to solutions of alkyl monoglycosides as well as of glucose and maltose.     

Enzymes Hosted in Reverse Micelles in Hydrocarbon Solution

Reverse micelles are spheroidal aggregates formed by certain surfactants in apolar media. In contrast to normal micelles in water, the polar head groups of the surfactant molecules are directed towards the interior of the aggregate and form a polar core which can solubilize water (the “water pool”); the lipophilic chains are exposed to the solvent. The water of the water pool exhibits properties that (depending on the mole ratio of water to surfactant) differ from those of bulk water. Surprisingly, these reverse micelles are able to solubilize in hydrocarbon solvents hydrophilic molecules, e.g., enzymes and even plasmids, that are much larger than the original water-pool diameter. These biopolymer-containing reverse micelles can be viewed as novel microreactors, whose physical properties can be controlled through the water content. Remarkable is the ability of enzyme-containing micelles to react with water-insoluble, hydrocarbon-soluble substrates, as in the example of lipoxygenase with linoleic acid.     

Recognition of Anions by Synthetic Receptors in Aqueous Solution

Natural anion binding systems achieve high substrate affinity and selectivity most often by arranging converging binding sites inside a cavity or cleft that is well shielded from surrounding solvent molecules by the folded peptide chain. Types of interactions employed for anion recognition are electrostatic interactions, hydrogen-bonding, and coordination to a Lewis-acidic metal center. In this review, successful strategies aimed at the development of synthetic receptors active in water or aqueous solvent mixtures are described. It is shown that considerable progress has been made during recent years in the development of potent anion receptors and that for every type of interaction used in nature for anion binding, corresponding synthetic models exist today. Representative examples of these systems are presented with a special emphasis on synthetic receptors whose characterization involved a detailed thermodynamic analysis of complex formation to demonstrate the important interplay between enthalpy and entropy for anion recognition in water.This revised version was published online in July 2005 with a corrected issue number.     

PdII and PtII Complexes with Amphiphilic Ligands: Formation of Micelles and [5]Rotaxanes with α‐Cyclodextrin in Aqueous Solution

[3]Pseudorotaxanes [ 1 (α‐CD)₂][X] (X=Cl, NO₃), prepared from reaction of an N‐alkylbipyridinium [4,4′‐bpy‐N‐(CH₂)₁₀OC₆H₃‐3,5‐(OMe)₂][X] ([ 1 ][X]) and α‐CD, react with M(NO₃)₂(en) (M=Pd, Pt; en=1,2‐ethylenediamine) in a 2:1 molar ratio to afford [5]rotaxanes [M{(4,4′‐bpy‐N‐(CH₂)₁₀OC₆H₃‐3,5‐(OMe)₂)(α‐CD)₂}₂ (en)][NO₃]₄ ([ 2 (α‐CD)₄][NO₃]₄, M=Pd; [ 3 (α‐CD)₄][NO₃]₄, M=Pt). A similar reaction of [ 1 ][Cl] with [M(NO₃)₂(en)] (M=Pd, Pt) produces amphiphilic Pd and Pt complexes, [ 2 ][NO₃]₄ and [ 3 ][NO₃]₄. Complexes [ 2 ][NO₃]₄ and [ 3 ][NO₃]₄ form micelles in the presence of small amounts of dyes (Nile red and pyrene) in water. The critical micelle concentration (CMC) was determined by the absorption peak of the dye, which is encapsulated in the micelles in solution. Micelle formation is confirmed by dynamic light scattering measurement of the solution and TEM (transmission electron microscopy) images of the micelles deposited from the solution. Addition of α‐CD to the aqueous solution containing these amphiphilic complexes results in degradation of the micelle structure and the formation of [5]rotaxanes, [ 2 (α‐CD)₄][NO₃]₄ and [ 3 (α‐CD)₄][NO₃]₄.     

Unstable Supramolecular Structure of [Bmim][BF4] in Aqueous Solution

To unravel the exact composition and structure of aggregates in an aqueous solution of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]), we performed static and dynamic light-scattering measurements, as well as transmission electron microscopy (TEM). Results from this work show that the aggregates are vesicles and unstable; herein, we discuss the driving force behind the self-assembly. Apart from the van der Waals forces and repulsive electrostatic interactions between adjacent cation clusters, the hydrogen-bonding forces as well as counterion effects might also contribute to this driving force. The information obtained here is useful for a better understanding of the vital role that aggregation behavior plays in the field of ionic liquid recovery, and its potential use in controlled release, drug delivery, and petroleum recovery.     

“Raft” Formation by Two‐Dimensional Self‐Assembly of Block Copolymer Rod Micelles in Aqueous Solution

Block copolymers can form a broad range of self‐assembled aggregates. In solution, planar assemblies usually form closed structures such as vesicles; thus, free‐standing sheet formation can be challenging. While most polymer single crystals are planar, their growth usually occurs by uptake of individual chains. Here we report a novel lamella formation mechanism: core‐crystalline spherical micelles link up to form rods in solution, which then associate to yield planar arrays. For the system of poly(ethylene oxide)‐block‐polycaprolactone in water, co‐assembly with homopolycaprolactone can induce a series of morphological changes that yield either rods or lamellae. The underlying lamella formation mechanism was elucidated by electron microscopy, while light scattering was used to probe the kinetics. The hierarchical growth of lamellae from one‐dimensional rod subunits, which had been formed from spherical assemblies, is novel and controllable in terms of product size and aspect ratio.     

三嵌段共聚物和两嵌段共聚物在水溶液中共混自组装成多室胶束结构的耗散粒子动力学模拟(英文)

利用耗散粒子动力学模拟研究了在水溶液中混合不同的线形三嵌段共聚物AxByCz和线形两嵌段共聚物AmBn对多室胶束的形貌多样性的影响.通过改变线形的三嵌段共聚物和两嵌段共聚物的链长来寻找多室胶束的形成条件.由线形三嵌段共聚物和线形两嵌段共聚物的不同混合形成的多室胶束结构是多种多样的,例如"蠕虫状"胶束、"汉堡包"胶束、"球上球"胶束、"核-壳-壳"胶束等等.多室胶束的整体形貌和内部结构的控制都可以从线形三嵌段共聚物和两嵌段共聚物的二元共混得到.为了表征获得的多室胶束结构,我们计算了密度图和成对分布函数图.在此工作中,可以获得和观察到复杂的多室胶束.结果表明,简单地混合线形的三嵌段共聚物和线形的两嵌段共聚物是一个控制多室胶束形貌和结构的有效方法,在工程实验中可以更简单更经济地形成多室胶束结构.因此,在设计新的多室胶束方面,聚合物共混仍然是未来值得更加关注的一个话题.     

Binding Selectivity of Macrocycle Ionophores in Ionic Liquids versus Aqueous Solution and Solvent‐free Conditions

The understanding of supramolecular recognition in room‐temperature ionic liquids (RTILs) is key to develop the full potential of these materials. In this work, we provide insights into the selectivity of the binding of alkali metal cations by standard cyclodextrin and calixarene macrocycles in RTILs. A direct laser desorption/ionization mass spectrometry approach is employed to determine the relative abundances of the inclusion complexes formed through competitive binding in RTIL solutions. The results are compared with the binding selectivities measured under solvent‐free conditions and in water/methanol solutions. Cyclodextrins and calixarenes in which the peripheral OH groups are substituted by bulkier side groups preferentially bind to Cs⁺. Such specific ionophoric behavior is substantially enhanced by solvation effects in the RTIL. This finding is rationalized with the aid of quantum mechanical calculations, in terms of the conformational features and steric interactions that drive the solvation of the inclusion complexes by the bulky RTIL counterions.