Pluronic嵌段共聚物F127和P123胶束对萘、蒽、芘的增溶

35℃时F127和P123在ccm后可生成内核PO成分分别为92.7%和94.5%的胶束,后者胶束内核体积为前者的2.8倍.稠环芳烃和空胶束的第一步缔合平衡常数K₁值均随萘、蒽、芘顺序逐渐增大.萘、蒽、芘在每个F127和P123胶束中的增溶量均随胶束内核体积增大而线性增加,每个PO基团对应的增溶量比十二烷基磺酸胶束内核中相同体积对应的增溶量约大近2倍.Pluronic胶束除与稠环芳烃间具有强相互作用力外,所形成的大内核是导致大增溶量的重要因素.     

胶束溶液增溶过程的高分辩NMR研究

本文用高分辨~1H-NMR谱, 研究了十二烷基硫酸钠(SDS)胶束水溶液对m-二甲苯和苯甲醇的增溶作用。结果表明, 增溶物浓度很低时, m-二甲苯和苯甲醇均吸附在胶束-水“界面”。随着浓度增加m-二甲苯增溶在胶束的“栅栏”层和内核中, 并沿SDS的烃链均匀分布。当浓度约为0.34摩尔分数时, 它沿烃链的增溶达到“饱和”, 开始进入胶束内核中心。苯甲醇主要增溶在“栅栏”层中, 其羟基靠近胶束-水“界面”, 苯基深入到与α-CH_2基相邻的五个亚甲基的位置。     

苯在Pluronic F127和P123胶束水溶液中的增溶动力学

发展了不分离胶束的增溶动力学数据分析模型,以此考察苯在F127和P123胶束水溶液中的增溶动力学行为.实验发现,这二种胶束增溶苯的速度较快,温度升高进一步促进了增溶.     

分子动力学模拟研究荧光分子芘在磺基甜菜碱胶束中的增溶

采用分子动力学模拟研究了荧光分子芘在磺基甜菜碱两性表面活性剂聚集体中的增溶现象．结果表明,芘分子自发地自溶液中增溶进入胶束疏水内核的栅栏层区域．当胶束溶液中芘分子的局部浓度增大时,两个芘分子可以同时增溶进胶束的栅栏层区域,此时两个芘分子形成π-π共轭堆积的激发态络合物．但是由于荧光分子之间的弱兀．兀相互作用,激发态络合物在胶束中是不稳定的,表现为两个芘分子的多次结合和分离．模拟表明,分子动力学方法可以在分子水平上研究荧光探针分子在表面活性剂胶束中的增溶位点,解释荧光分子在胶束中的动力学现象．     

二元Pluronic嵌段共聚物相互作用

用I2探针增溶分光光度法考察二元Pluronic两亲嵌段共聚物在水溶液中的胶束化行为,实验结果表明,对于分子PPO嵌段长度相近的P94/L92和F108/L92二元混合体系,这些分子在全部浓度比例范围内都发生相互作用,生成了混合胶束,由于这些分子的PEO嵌段长度不等,随着具有较短PEO嵌段的L92分子加入,P94/L92和F108/L92混合胶束外壳的EO基团数减少导致水化度降低。对于分子PPO嵌段长度不等的P94/L64二元混合体系,当溶液体当中L64的质量分数wL64<0.4时,由于P94/L64混合预胶束的形成,使P94分子在较高浓度时才生成单组分胶束,当wL64>0.4后,溶液中生成了P94/L64混合胶束,温度升高促进了胶束化行为。     

表面活性剂溶胀胶束：性能及应用

溶胀胶束是表面活性剂胶束增溶其它物质后使胶束膨胀的一种胶束状态,因其能显著提高难溶性物质的溶解度而备受关注。针对近年来对溶胀胶束的研究进展,综述了溶胀胶束的最大增溶量、增溶过程以及增溶后形貌尺寸的变化等问题,总结了影响胶束增溶作用的因素,厘清了溶胀胶束与微乳液的异同,介绍了溶胀胶束的应用,展望了其应用前景与发展方向。     

药物包载对两亲嵌段共聚物胶束形态的影响

以聚(ε-己内酯-b-L-丙交酯)/聚乙二醇单甲醚(P(CL-b-LLA)-b-mPEG)和聚(ε-己内酯-b-D,L-丙交酯)/聚乙二醇单甲醚(P(CL-b-DLLA)-b-mPEG)两种两亲嵌段共聚物为载体,选择了物理状态完全不同、而疏水性相近的吲哚美辛和维生素E为模型药物,研究了药物包载对高分子胶束形态的影响.发现两种药物在高分子胶束内部的增溶均会导致胶束形态发生显著改变,变化行为与胶束内核的结晶性和药物疏水性有关.另外,还研究了两种嵌段共聚物的载药性能,发现非结晶性疏水内核共聚物的药物包载率明显大于可结晶疏水内核的共聚物.     

稀土显色反应中的溶剂化效应及混合胶束作用

随着胶束增溶分光光度法的深入发展,发现在胶束增溶体系中,引入适量的有机溶剂或非离子表面活性剂,对体系有更强的增溶、增敏、增加稳定性等作用,即“溶剂化效应”及“混合胶束作用”。文     

聚乙二醇-聚乳酸共聚物胶束溶液的冷冻干燥及胶束体外释药动力学研究

合成了一系列亲水、疏水链段质量比例不同的聚乙二醇-聚乳酸(PEG-PLA)嵌段共聚物胶束, 并以两性霉素B为模型药物制备了载药胶束. 为获得稳定性良好的、可长期储存的载药胶束剂型, 对胶束进行了冷冻干燥. 使用不同浓度的糖类(包括甘露糖、海藻糖、葡萄糖)、泊洛沙姆188 (Pluronic F68)、聚乙二醇作为冻干保护剂, 以冻干产品的重分散性、冻干前后胶束的粒径及多分散性为指标评价各种保护剂的保护效果. 结果发现, 当嵌段聚合物中聚乳酸链段的质量百分比小于或等于聚乙二醇时, 糖类、Pluronic F68和PEG均可以起到有效的冻干保护作用; 而对于聚乳酸链段质量比例较大的共聚物胶束, 只有PEG和Pluronic F68能够起到较好的冻干保护作用. 对载药胶束体外释放研究表明, 聚合物胶束的体外释放缓慢, 符合一级动力学特征.     

温度对Pluronic嵌段共聚物胶束结构的影响

温度对Ｐｌｕｒｏｎｉｃ嵌段共聚物Ｆ１０８、Ｆ６８、Ｐ９４和Ｌ６４胶束结构影响的研究结果表明,随着温度上升,胶束外壳ＰＥＯ链的水化度急剧减小,胶束趋于形成聚集更为密实、尺寸较均匀的球形结构。在较高温度时,胶束内核基本上以ＰＰＯ链为主构成。     

芘在Pluronic两亲嵌段共聚物胶团中的增溶

用稳态荧光法研究芘（Py）在Pluronic两亲嵌段共聚物胶团水溶液中的增溶,结果表明共聚物分子中的PPO实际含量越大,越有利于Py的增溶。加入无机盐KCl导致生成了表面较少水化的较大胶团,并且由于KCl解离产生的离子使溶剂极性增加,这些因素促进了Py的增溶。     

Phase behavior and local dynamics of concentrated triblock copolymer micelles

We report a neutron-scattering study to characterize the ordering and local dynamics of spherical micelles formed by the triblock copolymer polyethylene oxide (PEO)--polypropylene oxide (PPO)--polyethylene oxide (Pluronic) in aqueous solution. The study focuses on two Pluronic species, F68 and F108, that have the same weight fraction of PEO but that differ in chain length by approximately a factor of 2. At sufficiently high concentration, both species undergo a sequence of phase changes with increasing temperature from dissolved chains to micelles with liquid-like order to a cubic crystal phase and finally back to a micelle liquid phase. A comparison of the phase diagrams constructed from small-angle neutron scattering indicates that crystallization is suppressed for shorter chain micelles due to fluctuation effects. The intermediate scattering function I(Q,t)I(Q,0) determined by neutron spin echo displays a line shape with two distinct relaxations. Comparisons between I(Q,t)I(Q,0) for fully hydrogenated F68 chains in D2O and for F68 with deuterated PEO blocks reveal that the slower relaxation corresponds to Rouse modes of the PPO segments in the concentrated micelle cores. The faster relaxation is identified with longitudinal diffusive modes in the PEO corona characteristic of a polymer brush.     

Micellar ordered structure effects on high‐resolution CE‐SSCP using Pluronic triblock copolymer blends

Pluronic F108 block copolymers have shown a great promise to achieve the desirable high resolution in the conformation‐sensitive separation of ssDNA using CE‐SSCP. However, fundamental understanding of the structures and properties of Pluronic matrix affecting the resolution is still limited. Unlike conventional gel‐forming homopolymers, Pluronic F108 block copolymers are amphiphilic macromolecules consisting of poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide) triblock copolymers, which are capable of forming a highly ordered micellar structure in aqueous solution. In this study, we have performed a series of experiments by blending different types of Pluronic polymers to control the formation of micelles and to study the correlation between separation and rheological characteristics of Pluronic gels affecting the resolution of CE‐SSCP. Our experiments have been specifically designed to elucidate how the micellar structure affects the resolution of CE‐SSCP upon altering the size uniformity and constituent homogeneity of the micelles. Our results suggest that uniformly sized micelle packing is the primary structural feature of Pluronic gel matrix for the high‐resolution separation, while the size and constituent of the micelle themselves need to be considered as secondary factors.     

Thermogelling properties of triblock copolymers in the presence of hydrophilic fe(3)o(4) nanoparticles and surfactants

We investigate the supramolecular structure formed by thermogelation of a triblock polymer in the presence of nanoparticles and surfactant using rheometry and small-angle X-ray scattering (SAXS). The triblock copolymer, nanoparticle, and surfactant used in this study are poly(oxyethylene-oxypropylene-oxyethylene), Pluronic F108, Fe(3)O(4) nanoparticles, and sodium dodecyl surfactant, respectively. Addition of 1-5 wt % of Fe(3)O(4) nanoparticle, of average particle size ～10 nm, in a weak template of F108 (15 wt %) shows a decrease in the onset of gelation temperature and dramatic alteration in the viscoelastic moduli. The nanocomposite samples show a linear viscoelastic regime up to 5% strain. The SAXS measurement shows that the intermicellar spacing of the supramolecular structure of pure F108 is ～16.5 nm, and the supramolecular structure is destroyed when nanoparticles and surfactants are incorporated in it. Further, the addition of anionic surfactant to nanocomposites leads to a dramatic reduction in the viscoelastic properties due to strong electrostatic barrier imparted by the surfactant headgroup that prevents the formation of hexagonally ordered micelles. Our results show that the thermogelation is due to the clustering of nanoparticles into a fractal network rather than a close-packed F108 micelles, in agreement with the recent findings in Pluronic F127-laponite systems.     

Time-resolved in situ studies of the formation of cubic mesoporous silica formed with triblock copolymers

The mechanism of formation of two different cubic mesoporous silica materials formed with Pluronic triblock copolymers is investigated with in situ time-resolved small-angle synchrotron X-ray scattering, in situ time-resolved 1H nuclear magnetic resonance, and time-resolved transmission electron microscopy. The materials studied are the micellar cubic (Imm) SBA-16 formed with Pluronic F108 and the bicontinuous cubic (Iad) silica material formed with Pluronic P103 and NaI. The formation mechanisms of the two cubic structures are shown to be dissimilar. For the Imm material, in the early stages of the synthesis, flocs of unordered micelles are observed, but areas where the micelles have started to order are also present. With time, there is an increase in order; however, there is a coexistence of unordered micelles and ordered material all through this study. The bicontinuous cubic silica is formed via a different path. The system is phase-separated already before the addition of the silica source, which implies that a concentrated phase is present, acting as the structure director of the Iad structure. The results are compared with earlier reports on the formation of the hexagonal SBA-15 material.     

Stabilization and activation of Pluronic micelles for tumor-targeted drug delivery

In order to be used as drug carriers, Pluronic micelles require stabilization to prevent degradation caused by significant dilution accompanying IV injection. This article studies three routes of Pluronic micelle stabilization. The first route was direct radical crosslinking of micelles cores which resulted in micelle stabilization. However, this compromised the drug loading capacity of Pluronic micelles. In the second route, a small concentration of vegetable oil was introduced into diluted Pluronic solutions. This decreased micelle degradation upon dilution while not compromising the drug loading capacity of oil-stabilized micelles. The third route was a novel technique based on polymerization of the temperature-responsive LCST hydrogel in the core of Pluronic micelles. The hydrogel phase was in a swollen state at room temperature, which provided a high drug loading capacity of the system. The hydrogel collapsed at physiological temperatures which locked the core of micelles thus preventing them from fast degradation upon dilution. This new drug delivery system was called Plurogel®. Phase transitions in Plurogel® caused by variations in temperature or concentration were studied by the EPR. The effect of Pluronic concentration in the incubation medium on the intracellular uptake of two anti-cancer drugs was studied. At low Pluronic concentrations, when the drugs were located in the hydrophilic environment, drug uptake was increased, presumably due to the effect of a polymeric surfactant on the permeability of cell membranes. In contrast, when the drugs were encapsulated in the hydrophobic cores of Pluronic micelles, drug uptake by the cells was substantially decreased. This may be advantageous in the prevention of undesired drug interactions with normal cells. Ultrasonication enhanced intracellular drug uptake from dense Pluronic micelles. These findings permitted the formulation of a new concept of a localized drug delivery.     

Effects of poloxamer polydispersity on micellization in water

The poloxamer 284 (Pluronic P94) is a triblock copolymer of poly(ethylene oxide) and poly(propylene oxide). P94 and fractions of P94 obtained after centrifugation at temperatures where solutions contain both dissolved unimers and micelles have been investigated by differential scanning calorimetry, mass spectrometry, and NMR. The results show that the P94 sample is heterogeneous with respect to both chemical composition and molar mass. The first micelles formed, when the temperature is increased, contain poloxamers with a significantly higher propylene oxide content and a higher molar mass in agreement with theoretical predictions. The characteristic temperatures of micellization, sphere-to-rod, and phase separation transitions observed in thermograms are influenced by polydispersity, which results in broader transitions.