芘从H2O/DMF溶剂向两亲嵌段共聚物平头胶团增溶

发展了从荧光发射谱计算芘（Py）增溶量的方法,以此研究Py从H2O／DMF混合溶剂向PS-b-PAA二嵌段共聚物平头胶团的增溶．实验结果表明,混合溶剂中水含量强烈影响Py的增溶,随水含量增加,Py增溶量增大．结合公式和分布系数,计算并讨论了Py的增溶等温线．理论处理给出了从实验荧光强度直接计算Py在胶团和溶剂相间分布系数的方法     

芘从H_2O/DMF混合溶剂向聚苯乙烯/聚丙烯酸二嵌段共聚物平头胶团增溶(Ⅱ)

混合溶剂水含量强烈影响芘从Ｈ２Ｏ／ＤＭＦ混合溶剂向聚苯乙烯／ 聚丙烯酸二嵌段共聚物平头胶团的增溶,随着水含量增加而明显增大了芘和胶团内核ＰＳ间的结合力,促进了芘的增溶。实验结果表明,增加混合溶剂极性组分是实现有效增溶的一种简便方法。     

芘从H2O／DMF混合溶剂向聚苯乙烯／聚丙烯酸二嵌段共聚物平头胶 …

混合溶剂水含量强烈影响芘从Ｈ２Ｏ／ＤＭＦ混合溶剂向聚苯乙烯／聚丙烯酸二嵌段共聚物平头胶团的增溶,随着水含量增加而明显增大了芘和胶团内核ＰＳ间的结合力,促进了芘的增溶。实验结果表明,增加混合溶剂极性组分是实现有效增溶的一种简便方法。     

增溶甲苯对聚氧乙烯-聚氧丙烯嵌段共聚物胶团的影响

用动态光散射, 测定聚氧乙烯-聚氧丙烯嵌段共聚物水溶液胶团增溶不同量的甲苯后, 其平均流体力学半径R_h的变化, 以及温度对它们的影响。实验结果表明, 25 ℃时胶团水化度高, R_h数值大, 增溶不同量的甲苯对R_h的影响较小。温度升高,胶团的水化度降低, R_h变小, 当温度接近浊点, 水化作用降至最低。因温度升高引起的胶团聚集数增加以及增溶的甲苯进入胶团内部的胀大作用, 使R_h随增溶量增加近于线性的上升。     

Pluronic嵌段共聚物F127胶团对布洛芬的增溶(英文)

研究了PluronicF127胶团溶液对药物布洛芬(IBU)的增溶作用.通过芘探针荧光法测定了不同温度下F127在水溶液和0.01mo·lL-1pH7.4磷酸盐缓冲生理(PBS)溶液中的临界胶束浓度(cmc),采用高效液相色谱(HPLC)测定了F127溶液中布洛芬的溶解度,并依据公式计算了增溶参数(摩尔增溶量c和胶团-水分配系数K),考察了温度、溶剂和F68的加入对F127胶团化行为及其对布洛芬增溶作用的影响.结果表明:布洛芬的溶解度随F127质量分数的提高线性增加;随着温度升高,cmc急剧下降,胶团内核的疏水性增强,χ和K稍有增大;与水溶液相比,在PBS溶液中cmc减小,χ几乎不变,K显著降低;F68的加入对F127胶团的性质几乎无影响,对增溶的影响也不明显.对增溶参数的分析表明,K反映的是药物布洛芬的性质,χ则可反映嵌段共聚物F127的溶解效能,并证实了布洛芬是通过F127胶团的内核和栅栏层而实现增溶的.     

C12-s-C12•2Br在正庚烷中反胶团形成及增溶水特性

在助表面活性剂正己醇存在下, 季铵盐Gemini表面活性剂C12-s-C12•2Br(s=2、3、4、5、6、8、12)在正庚烷中形成了反胶团. 以水增溶法测定了临界反胶团浓度cmcw, 这些cmcw均分别小于它们在水中生成正胶团的临界浓度cmcaq. cmcw随s的变化规律与cmcaq随s的变化规律类似, 在s=4时出现极大值. 由水增溶法和电导法获得的反胶团饱和增溶水量(mw或mc)约在s=5时出现最大值. 这些现象被归结为联接链构型的变化.     

NaBr对C12-s-C12•2Br/氯仿体系中反胶团增溶水能力的影响

近红外(NIR)光谱技术可用于表征氯仿体系中反胶团增溶水的能力. 对于C12-s-C12•2Br (s=2, 3, 4, 5, 6, 8)系列, 不论体系是否含有NaBr电解质, 由于具有较短联接链的表面活性剂易形成较大的反胶团, 其增溶水的能力随着联接链长度增加而降低. 与未含NaBr电解质的体系相比, 当体系中存在NaBr电解质时所形成的反胶团增溶水能力降低.     

聚醚型表面活性剂水溶液中胶团的生成

属于ABA型嵌段共聚物(A为聚氧乙烯,B为聚氧丙烯)的聚醚型表面活性剂分子在水中是否生成胶团,文献报道的结果迥异,临界胶团浓度值随测定方法不同出入很大.某些AB型或ABA型嵌段共聚物在选择性有机溶剂中表现出异常胶团化行为,但对于水体系迄今未见报道.本文以多种实验手段研究了典型的聚醚型表面活性剂Pluronic L-64水溶液的胶体与表面性质.结果表明,与通常的表面活性剂不同,随着温度或浓度的变化,L-64溶液中生成单分子胶团或者缔合胶团.在两者的转变间,首次观察到了水体系中的异常胶团化现象.     

PLA-mPEG嵌段共聚物胶团的制备及其表面张力

PLA-mPEG嵌段共聚物胶团的制备及其表面张力;丙交酯;甲氧基聚乙二醇;嵌段共聚物;纳米胶团;表面张力     

胶束介质中丁二酮增溶位点的室温燐光碎灭法研究

采用丁二酮室温光猝灭法研究了胶束介质中丁二酮的增溶位点，通过研究4种不同荷电和不同亲水亲脂性的光猝灭剂以及盐效应等对Stern－Volmer常数的影响，表明了二酮在SDS、CTAB的胶束中是增溶在胶团的栏栅并靠近离子头基一侧和头基／水界面附近，而在CTAB胶束中更加趋向于胶团外部头基附近．     

Aggregation behavior of pluronic triblock copolymer in 1-butyl-3-methylimidazolium type ionic liquids

Three amphiphilic poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) ethers triblock copolymers, denoted Pluronic L61 (PEO3PPO30PEO3), Pluronic L64 (PEO13PPO30PEO13), and Pluronic F68 (PEO79PPO30PEO79) were shown to aggregate and form micelles in ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). The surface tension measurements revealed that the dissolution of the copolymers in ILs depressed the surface tension in a manner analogous to aqueous solutions. The cmcs of three triblock copolymers increase following the order of L61, L64, F68, suggesting that micellar formation was driven by solvatophobic effect. cmc and gamma cmc decrease with increasing temperature because hydrogen bonds between ILs and hydrophilic group of copolymers decrease and accordingly enhance the solvatophobic interaction. Micellar droplets of irregular shape with average size of 50 nm were observed. The thermodynamic parameters DeltaGm0, DeltaHm0, DeltaSm0 of the micellization of block copolymers in bmimBF4 and bmimPF6 were also calculated. It was revealed that the micellization is a process of entropy driving, which was further confirmed by isothermal titration calorimetry (ITC) measurements.     

Melt, hydration, and micellization of the PEO-PPO-PEO block copolymer studied by FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was used to study the conformational changes of the polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) block copolymer, Pluronic P104, in a large concentration range in a polymer-water system as a function of temperature. The melt in which the conformational transition of the PEO blocks occurs gives remarkable changes in the spectral behavior. A small amount of water in Pluronic P104 can induce the PEO block amorphism. The addition of more water only swells the PEO dominant region and gives no significant difference in the conformational structure of the block copolymer in the ordered phases of Pluronic P104-water mixtures. The PPO blocks of Pluronic P104 are hydrated only in a condition of lower temperature and higher water content. The temperature dependent micellization of Pluronic P104 in water was analyzed by a FTIR spectroscopic method. The appearance of the symmetric deformation band of the anhydrous methyl groups at temperature below the CMT indicates the existence of a hydrophobic microenvironment. The appearance of the symmetric deformation band of the hydrated methyl groups at higher temperatures indicates that the micellar core must contain some amount of water. The results of FTIR data show that the proportion of the anhydrous methyl groups increases and water content in the micellar core decreases during the micellization process.     

Thermodynamics of temperature-sensitive polyether-modified poly(acrylic acid) microgels

The temperature-induced structural changes and thermodynamics of ionic microgels based on poly(acrylic acid) (PAA) networks bonded with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) (Pluronic) copolymers have been studied by small-angle neutron scattering (SANS), ultra-small-angle neutron scattering (USANS), differential scanning calorimetry (DSC), and equilibrium swelling techniques. Aggregation within microgels based on PAA and either the hydrophobic Pluronic L92 (average composition, EO8PO52EO8; PPO content, 80%) or the hydrophilic Pluronic F127 (average composition, EO99PO67EO99; PPO content, 30%) was studied and compared to that in the solutions of the parent Pluronic. The neutron scattering results indicate the formation of micelle-like aggregates within the F127-based microgel particles, while the L92-based microgels formed fractal structures of dense nanoparticles. The microgels exhibit thermodynamically favorable volume phase transitions within certain temperature ranges due to reversible aggregation of the PPO chains, which occurs because of hydrophobic associations. The values of the apparent standard enthalpy of aggregation in the microgel suspensions indicate aggregation of hydrophobic clusters that are more hydrophobic than the un-cross-linked PPO chains in the Pluronic. Differences in the PPO content in Pluronics L92 and F127 result in a higher hydrophobicity of the resulting L92-PAA-EGDMAmicrogels and a larger presence of hydrophobic, densely cross-linked clusters that aggregate into supramolecular structures rather than micelle-like aggregates such as those formed in the F127-PAA-EGDMA microgels.     

Light scattering study of solubilization of organic molecules by block copolymer micelles in aqueous media

Block copolymers, when dissolved in a selective solvent, form spherical micelles. These micelles can selectively solubilize organic molecules otherwise insoluble in the pure solvent. In this study, we report solubilization of organic molecules by styrene-methacrylic acid block copolymer micelles in aqueous buffers. A light scattering technique was developed to determine the extent of micellar solubilization. Our results indicate that the extent of micellar solubilization depends on the chemical nature of organic molecules, specifically, on the interactions between the organic compound and polystyrene. A thermodynamic model has been developed to describe micellar solubilization. The theoretical calculation agrees reasonably well with the experimental results for two micellar samples examined. ©1995 John Wiley & Sons, Inc.     

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.     

Stabilization of lysozyme-incorporated polyion complex micelles by the omega-end derivatization of poly(ethylene glycol)-poly(alpha,beta-aspartic acid) block copolymers with hydrophobic groups

To improve the stability of lysozyme-incorporated polyion complex (PIC) micelles in physiological condition, three types of hydrophobic groups, including phenyl (Phe), naphthyl (Nap), and pyrenyl (Py) terminal groups, were separately introduced to the omega-end of poly(ethylene glycol)-poly(alpha,beta-aspartic acid) block copolymers (PEG-P(Asp)). The goal was to enhance association forces between the enzyme, lysozyme, and PEG-P(Asp) carriers. Introduction of these hydrophobic groups significantly decreases micellar critical association concentration and increases the micellar tolerability against increasing NaCl concentrations. Particularly, PIC micelles formed from PEG-P(Asp) with Py groups was most stable against increasing NaCl concentrations up to 0.1 M. Significant deviation from a spherical shape for the micelles was also observed for the PEG-P(Asp)-Py system, consistent with an increased association number.     

Effects of block size of pluronic polymers on the water structure in the corona region and its effect on the electron transfer reactions

Effects of constituent block size of triblock copolymers on the nature of the water molecules in the corona region of their micelles have been investigated using time-resolved fluorescence measurements. The physical nature of the water molecules in the micellar corona region of the block copolymer, Pluronic F88 ([ethylene oxide (EO)]103-[propylene oxide (PO)]39-EO103), has been studied using a solubilized coumarin dye. Solvent reorientation time and rotational correlation time have been measured and compared with another block copolymer, Pluronic P123 (EO20-PO70-EO20), which has a different composition of the constituent PO and EO blocks. It is noted that due to the presence of larger number of EO blocks in F88 as compared with P123, the corona region of the former micelle is more hydrated than that of the latter. The solvent reorientation time and rotational correlation time are found to be relatively shorter for F88 as compared with P123. This indicates that the water molecules in the corona of the F88 micelle are more labile than those of P123, which is also supported from the estimated number of water molecules associated with each EO unit, measured from the size of each type of micelle and its aggregation number. To understand the effect of block size on the chemical reactions in these microheterogeneous media, electron transfer reactions have been carried out between different coumarin acceptors and N, N-dimethylaniline donor. The electron transfer results obtained in F88 micelles have been compared with those obtained in P123, and the results are rationalized on the basis of the relative hydration of the two triblock copolymer micelles.     

Mixed micelle formation with hydrophobic and hydrophilic Pluronic block copolymers: implications for controlled and targeted drug delivery

Pluronic block copolymers offer affluent phase behavioral characteristics and are extensively investigated for drug delivery applications. Hydrophobic Pluronics produce larger aggregates whereas hydrophilic Pluronics often generate small-sized micelles in aqueous milieu. To overcome the limitations and combine the advantages of different kinds of Pluronics the mixing of such two types of Pluronics is studied here, especially for hydrophobic Pluronic L81 and relatively hydrophilic Pluronic P123. Critical micelle concentration (CMC) of the developed binary mixtures was 0.032 mg/ml as evidenced from pyrene fluorescence spectroscopy and is located in between that of the individual Pluronics. Dynamic light scattering (DLS) showed very small particle sizes (～20 nm) and low polydispersity indices for most of the mixed micelles. Transmission electron microscopy (TEM) demonstrated spherical shape of micelles. Based upon the ratio of hydrophobic and hydrophilic Pluronics, dispersions of varied stability were obtained. With 0.1/1.0 wt.% and 0.5/3.0 wt.% of Pluronic L81/P123, stable dispersions were obtained. Stability was assessed from turbidity measurement, size analysis and clarity of dispersion on standing. Micelles were also found to be stable in bovine serum albumin (BSA) solution. Mixed micelles showed fairly high entrapment efficiency, loading capacity and sustained release profile for aceclofenac (Acl), a model hydrophobe. Presence of salt lowered Acl solubilization in micelles. Thermodynamic parameters for Acl solubilization in mixed micelles revealed high partition coefficient values and spontaneity of drug solubilization. Thus, the developed novel mixed micelles hold promise in controlled and targeted drug delivery owing to their very small size, high entrapment efficiency and stability.     

温度对萘在Pluronic胶束水溶液中增溶的影响

研究结果表明 ,温度升高促使Pluronic分子形成更加疏水并且具有较大内核的胶束 ,使萘和胶束内核的亲和力增强 ,从而促进萘的增溶。在所考察的F1 0 8和P94二种Pluronic胶束体系中 ,温度对增溶的促进作用 ,前者比后者更为明显。