智能性水凝胶

“智能”材料具有传感、处理和执行功能，水凝胶作为智能材料其应用前景良好。本文综述了智能水凝胶的近期研究发展，以Ｆｌｏｒｙ的溶胀理论着重探讨了刺激响应性，并介绍了化学机械现象及凝胶相转变。     

Incorporation of a lipophilic series,as coenzyme Q Homologs,din phospholipid vesicles

The incorporation of Coenzyme Q† homologs into phospholipid vesicles to achieve a concentration close to the quinone content of mitochondria has been studied with different methods. The results obtained can be summarized as follows: (a) stirring does not lead to comparable incorporation of the various CoQs tested; (b) ultrasonic irradiation results in a homogeneous incorporation both of the naturally occurring homologs of Coenzyme Q (polyisoprenoid chainlength ranging from ten to six units) and of the nonphysiological shorter chain homologs; (c) ethanol injection, which is a simple, rapid, and inexpensive technique, gives results comparable to those obtained by ultrasonication.     

Amphiphilic bipolar duplex α-cyclodextrin forming vesicles

We synthesized a duplex cyclodextrin with two aliphatic links and functionalized with eight pentyl ethers orientated towards the centre of the duplex. We found that this molecule self-assembled in water to form stable vesicles with a diameter within the range 1-10 μm.     

新型阴离子型温敏水凝胶

新型阴离子型温敏水凝胶王昌华,曹维孝（北京大学化学与分子工程学院,北京,１００８７１）关键词温敏水凝胶,溶胀比,Ｎ－异丙基丙烯酰胺１９８４年Ｔａｎａｋａ等人［１］发现Ｎ－异丙基丙烯酰胺（ＮＩＰＡ）与Ｎ,Ｎ－亚甲基双丙烯酰胺（ＭＢＡ）的微交联共聚体,在...     

Slow release from gels in various solvents: a fluorescence study

A novel in situ steady state fluorescence experiment was performed for studying slow release processes in gels formed by free radical cross-linking copolymerization of methyl methacrylate and ethylene glycol dimethacrylate. Gels were prepared at 75 °C with pyrene (P_y) as a fluorescence probe. After drying these gels, slow release experiments were performed in various solvent with different molar-volume, V and solubility parameters, δ at room temperature by real-time monitoring of the P_y fluorescence intensity. Slow release diffusion coefficients (D) were measured and found to be in between 0.23×10⁻⁶ and 2.06×10⁻⁶ cm² s⁻¹ depending on the solvent used.     

Modulation of interaction of polycations with negative unilamellar lipid vesicles

Interactions of small unilamellar negative vesicles composed of diphosphatidylglycerol (cardiolipin, CL²⁻), 20 mol%, and phosphatidylcholine (egg yolk lecithin, EL), 80 mol%, with various cationic polymers (CP) derived from poly(4-vinylpyridine) (PVP) were studied in water and water–salt solutions by means of photon correlation spectroscopy, microelectrophoresis, conductometry, and fluorescence techniques. The linear charge density and hydrophilic lipophilic balance of CPs were varied by quaternization of PVP with various amounts of different alkyl bromides (ethyl-(2), heptyl-(7), dodecyl-(12), cetyl-(16)). Substantial differences were observed in the behavior of exhaustingly N-ethylated PVP (CP2) and PVP N-ethylated to 50 mol% (CP2(50)) or 30 mol% (CP2(30)). All of them adsorb to the CL²⁻/EL vesicle membrane, neutralizing the surface negative charge and causing aggregation of the vesicles. However, CP2, a polycation with a maximum linear charge density, strongly enhances transfer of the negative lipid ions from the inner to outer bilayer leaflet, while CP2(50) and CP2(30) do not. Adsorbed CP2 does not disturb integrity of the vesicle membrane and can be completely removed from the surface of aggregated vesicles by adding a simple salt (NaCl) or a negative linear polyelectrolyte (polyacrylic acid (PAA) sodium salt). Such removal is followed by release of the original vesicles. In contrast to that, adsorbed CP2(50) or CP2(30) produce some leak through the lipid bilayer and cannot be completely desorbed either by increasing ionic strength or adding an excess of PAA. The probable reason of these differences is discussed. PVP partially N-alkylated with dodecyl or cetyl bromides (3 mol%) and then completely N-ethylated (CP2,12 and CP2,16), also having a maximum linear charge density, adsorbs to the negative vesicle surface as a result of both electrostatic binding and hydrophobic interaction. Bulky hydrocarbon pendant groups incorporate into the inner bilayer compartment. Similarly to CP2(50) and CP2(30), CP2,12 and CP2,16 cannot be removed from the surface either by adding the simple salt, or an excess of PAA. However, in contrast to CP2(50) and CP2(30), the polycations with the bulky hydrocarbon pendant groups do not cause any leak through the vesicle membrane. Finally, we have succeeded to prepare the ternary vesicles also composed of 20 mol% of CL²⁻, but partially replacing EL for polyoxyethylene 20 cetyl ether (Brij 58) (up to 30 mol%). The CL²⁻/EL/Brij vesicle carries a hydrophilic corona formed by polyoxyethylene chains exposed into water, while hydrophobic cetyl radicals are incorporated in the lipid bilayer. The CL²⁻/EL/Brij vesicles adsorb all studied CPs similar to the binary CL²⁻/EL vesicles. This means that polyoxyethylene corona is permeable for polycationic species restricting neither electrostatic binding nor incorporation of bulky hydrocarbon groups of CP2,16 into the membrane. However, the corona effectively stabilizes the CP-vesicle complexes against aggregation when the membrane surface is neutralized.     

化学改性大豆蛋白凝胶溶胀过程规律的研究

将大豆蛋白(SPI)经预热处理、EDTAD酰化和戊二醛交联,制备出改性大豆蛋白凝胶.通过红外与化学法研究了改性大豆蛋白分子的结构变化,结果表明,经EDTAD改性,大豆蛋白分子的侧链基团和分子链构象均发生变化;侧链的游离氨基与EDTAD发生酰化反应,为蛋白质分子链引入羧基;基团分析数据显示,改性大豆蛋白分子中游离氨基数减少,羧基数增加,增加的羧基数与减少的氨基数之比约为3:1.研究了改性大豆蛋白凝胶的溶胀率变化,并对溶胀数据进行数学处理,分析了不同mEDTAD:mSPI的凝胶的溶胀过程规律,结果显示,mEDTAD:mSPI为0,0.05,0.1和0.2的改性大豆蛋白凝胶在水中的溶胀率为24.2,54.01,87.27和95.87,说明分子链引入一定量的EDTAD使凝胶溶胀率增大;其溶胀特征指数为0.5,表现为Fickian扩散.研究了改性凝胶在不同pH下的溶胀过程规律,结果显示,在pH4.30和6.08时,凝胶溶胀特征指数n范围是0.5n1,表现为non-Fickian扩散,而在碱性pH10.04,凝胶特征溶胀指数为0.5,仍表现为Fickian扩散.改性大豆蛋白凝胶溶胀率对pH变化具有敏感性,其溶胀-消溶过程曲线呈"W"形,显示凝胶具形状记忆功能.     

聚丙烯酰胺纳米复合水凝胶研究进展

传统化学交联的聚丙烯酰胺(PAM)水凝胶由于力学性能较弱,其应用范围受到很大限制。与之相比,采用纳米复合技术制备的PAM纳米复合(NC)水凝胶,不仅大幅提高了力学性能,而且在溶胀率等方面也有明显的提高。本文结合该领域近年来的研究进展,将PAM NC水凝胶分为纯物理交联和化学物理交联相结合两类,重点讨论了NC水凝胶在力学性能方面的研究结果,对溶胀率等其它方面的性能也进行了综合论述。     

Synergism and polymorphism in mixed surfactant systems

Mixed surfactant systems have been, for a long time, one of the favorite areas for experimental studies on interfacial and bulk properties of surfactants. Beyond the well-known synergistic properties, with relevance to technical applications, recent studies increasingly focus on the bulk aggregation behavior. As more systematic and detailed experimental data is collected (for example, by use of scattering and direct imaging techniques), increasingly refined theoretical models are developed. Most references reviewed here clearly show both the trends. Topics such as micellar growth, micelle-to-vesicle transition and equilibrium vesicle formation in dilute systems (in particular in catanionic systems) continue to expand and sometimes pose challenges to conventional notions of surfactant self-organization. As the rich polymorphism of mixed aggregates is unraveled, the possibilities of using them for broader goals also increase (e.g. mesoporous materials and polymer-aggregate gels).     

亲水/疏水半互穿网络凝胶对温度的响应

研究了一种亲水/疏水型半互穿网水凝胶（PAAc/QPVPD gels）对温度的刺激响应.在弱酸性或弱碱性（pH=7.5）溶液中,该凝胶的溶胀比在低温区（< 28 ℃）随温度的升高微微增大,约在28 ℃出现最大值,然后随温度升高而迅速减小,温度约为32.5 ℃时溶胀比趋于最低值.这主要是由于聚丙烯酸网络(PAAc)中氢键的解离与疏水改性聚电解质N-正十二烷基聚（4-乙烯吡啶）溴化盐(QPVPD)的疏水相互作用共同引起的.     

Characterization of polymeric vesicles of poly(sodium 11-acrylamidoundecanoate) in water

A polysoap poly(sodium 11-acrylamidoundecanoate) was synthesized from sodium 11-acrylamidoundecanoate in water. The molecular weight of the polymer was determined by gel permeation chromatography and static light scattering techniques. Fluorescence probe studies in water have suggested the formation of hydrophobic domains within the same polymer chain. The microenvironment of the hydrophobic domains is highly ordered. The packing of the hydrocarbon chains in the hydrophobic domains formed by intra-chain association increases upon decrease of pH. The transmission electron micrograph revealed large vesicular aggregates in dilute aqueous solution. Temperature-dependent fluorescence anisotropy of the 1,6-diphenyl-1,3,5-hexatriene probe demonstrated stability of the vesicles.     

Solubilization kinetics of phospholipid vesicles by sodium taurocholate

The solubilization kinetics of phospholipid vesicles, about 100 nm in diameter and composed of egg phosphatidylcholine (EPC) and EPC/cholesterol in molar ratio 7/3, by sodium taurocholate (TC) used as a model bile salt were investigated by monitoring the turbidity at 500 nm and by quasielastic light scattering (QELS). The solubilization process was found to be dependent on the rate of TC addition. Although the solubilization profiles were identical whatever the rate of TC addition, an increase in the amount of TC needed to solubilize phosphatidylcholine liposomes was observed at higher rates. These results suggest that at low TC concentrations the permeability of the membrane to taurocholate is the rate-limiting step of the solubilization. In the case of cholesterol-containing vesicles, the effect of the rate of addition of TC was observed only at the solubilization characteristic points, called B and C, corresponding to a sharp decrease in the turbidity. This suggests that cholesterol greatly reduces the permeability of the membrane. In addition, the kinetic process was found to be independent of the micellar concentration of the detergent added to the aqueous medium, indicating that the solubilization of liposomes by TC was independent of the initial state of aggregation of the detergent. The calculated values of lipid/TC aggregates and of the partition coefficient show that the kinetic effect observed at high TC concentrations prior to complete solubilization might also be due to the diffusion of the detergent into the membranes. This gives rise to the differences in composition of the aggregates as a consequence of the variation in the rate of TC addition. In addition, QELS scattered intensity variations confirm the presence of a kinetic process for the solubilization of liposomes by TC. In conclusion, our results suggest that solubilization of lipid vesicles by TC is governed by kinetic parameters that might be controlled by liposome membrane permeability at low TC concentrations and by the lateral diffusion of the detergent into aggregates at higher TC concentrations.     

Preparation of dehydrated powder of hemoglobin vesicles

The carbonyl hemoglobin (CO-Hb), which was used to prevent denaturation (metHb) during the preparation of samples, was encapsulated into lipid vesicles constituted from unsaturated phospholipid, cholesterol and unsaturated fatty acid. Unsaturated components were polymerized by γ-irradiation to enhance the stability of bilayer membrane. An aqueous dispersion of resulting Hb vesicles was freeze-dried in the presence of saccharides (50–200 mM) to obtain a dehydrated powder of Hb vesicles. Change in the vesicle size, the leakage of encapsulated Hb and the oxidation of Hb to metHb were not observed. Therefore, the long-term storage of Hb vesicles can be realized as a dry powder.     

Raman spectroscopy for quantification of water-to-lipid ratio in phospholipid suspensions

In this paper, a way of quantification of the water-to-lipid ratio in aqueous suspensions of phospholipid vesicles by Raman spectroscopy is suggested. We measured the ratio of Raman intensities of the OH stretching band and the symmetric CH₂-stretching mode for series of water suspensions of different phosphatidylcholines with varied water-to-phospholipid ratio. It is shown that there is a simple linear relation between the ratio of Raman intensities and the water-to-lipid ratio if the number of CH₂ groups in the hydrocarbon chains is taken into account. The proportionality coefficient of this relation is determined for the gel and fluid phases of phospholipids.     

Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh₂(OH-bdc)₂]₁₂, a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc=5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh₂(OH-bdc)₂]₁₂ with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Na_x[Rh₂₄(O-bdc)_x(OH-bdc)_24-x], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.     

Subnanometer size uncapped quantum dots via electroporation of synthetic vesicles

The very rapid, usually diffusion-controlled, self-aggregation of nascent molecules of semiconductors (MX) or metals (M) in solution represents an experimental challenge for arresting the growth of the particles at a desired size. Unfortunately, the typical remedy used, namely capping of the clusters with a protective coating, alters their intrinsic electronic and optical properties. An additional defect of capping's virtue is that it prevents the observation of further cluster growth—which is especially important in the subnanometer (molecular) size regime, where particle growth is associated with dramatic changes in structure, surface states, and transition energy.

We have developed a novel method for the preparation of subnanometer size uncapped quantum dots, which also allows the monitoring of their growth up to several hundreds of nanometer in diameter. The essence of the method is the initial encapsulation of the metal ion (M⁺) in synthetic vesicles (liposomes) and the placement of the anion (X⁻) in the bulk solution. Exposure of the suspension to a rectangular pulse of a high-voltage homogenous electric field E of suitable intensity and duration causes the formation of transient pores in the vesicle's bilayer (electroporation). A fraction of the metal ions that are ejected through the pores react with the anions in the bulk, and the freshly created monomers (MX) adsorb on the exterior surface of the vesicle. On the vesicle surface, the self-aggregation is slowed down to the hour and day timescales which allows for convenient spectral monitoring of the growth of the clusters.

The discussion will focus on the behavior of vesicles in an electric field, the mechanism of electroporation, and our experimental and density functional theoretical findings of previously unobserved, unusual spectroscopic properties of subnanometer size AgBr, CdS, PbS, ZnS and gold quantum dots.     

Nanometre-sized molecular oxygen sensors prepared from polymer stabilized phospholipid vesicles

Nanometre-sized, chemically-stabilized phospholipid vesicle sensors have been developed for detection of dissolved molecular oxygen. Sensors were prepared by forming 150 nm phospholipid vesicles from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or DOPC doped with small (<1%) mole percentages of 1,2-dioleoyl-sn-glycero-3-phosphoethanol amine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (NBD-PE). Sensors were stabilized via cross-linking polymerization of hydrophobic methacrylate monomers partitioned into the hydrophobic interior of the DOPC bilayer. The resultant unilamellar, nanometre-sized, polymer-lipid vesicles are spherical, biocompatible and protect sensing components that are loaded into the aqueous interior of the vesicle from interfering species in the exterior environment. For O(2) detection, the oxygen-sensitive fluorescent dye, tris(1,10-phenanthroline)ruthenium(II) chloride (Ru(phen)(3)) was encapsulated into the aqueous interior of the polymerized phospholipid vesicle. NBD-PE was introduced into the phospholipid bilayer of the sensor as a reference dye, allowing ratiometric sensors to be constructed. The resultant sensors show high sensitivity, excellent reversibility and excellent linearity over a physiological range of dissolved oxygen concentrations. These results suggest that polymerized phospholipid vesicle sensors can be used for monitoring intracellular O(2) dynamics.     

Self-assembly of vesicles from the stacking of a dipodal F?H-N hydrogen bonded arylamide foldamer

In this paper, we report the synthesis and self-assembling behavior of an F?H-N hydrogen bonding-induced arylamide-based dipodal foldamer. SEM, AFM, TEM, and XRD studies reveal that this preorganized oligomer stacks to form vesicles in methanol-chloroform (10-70%) binary solvents due to the strong stacking interaction of the folded segments and the supramolecular polymeric feature of the dipodal molecule in the stacked state. In contrast, a simple folded molecule can give rise to vesicles only when the chloroform content is 45-55%.     

Formation of polymer vesicles by amphiphilic fluorosiloxane graft copolymers in solution

Amphiphilic fluorosiloxane graft copolymers with a poly(dimethylsiloxane)(PDMS) backbone,a hydrophobic fluorosiloxane side-chain and three hydrophilic poiyether side-chains were synthesized by hydrosilation reaction in this work.The micellization of amphiphilic graft copolymers in the water/ethanol solvent system was investigated,and vesicles with different size were formed after the self-assembly system was aged for different time.     

Synthetic membranes (vesicles) in inorganic ion analysis: a review

Vesicles are structures of amphiphile molecules occurring through a self-aggregation process at the molecular or nano scale level with a large structural variety and diverse properties providing a reaction environment for chemical reactions that resembles that of natural systems. Their high versatility and recognized utility in various applications have triggered a interdisciplinary scientific endeavor over their formation, characterization and potential applications with impressive results. However, in the vastness of applications surrounding vesicular structures, their utility in analytical chemistry has only received minor attention. Notwithstanding, studies demonstrating their potential as colorimetric or fluorescence sensors, extraction solvents of inorganic ions or their chelates and stationary phase modifiers in liquid chromatography have appeared. To this end, this article aims to present for the first time the analytical chemistry aspects behind the use of vesicle media with special emphasis on the detection and determination of inorganic ions and encourage further research on this promising field of analytical science.