PEO-PPO-PEO水溶液体系胶束化及凝胶化行为的耗散粒子动力学模拟

采用耗散粒子动力学(Dissipative particle dynamics, DPD)模拟方法研究了三嵌段共聚物聚氧乙烯-聚氧丙烯-聚氧乙烯(PEO-PPO-PEO)的胶束化和凝胶化行为. 通过模拟得到了F127(EO₉₉PO₆₅EO₉₉)水溶液的临界胶束浓度和临界凝胶浓度. 结果发现, 在298 K、 质量分数低于40%时, F127水溶液中形成的胶束形状均为球形. 此外,进一步研究了亲水嵌段长度对胶束结构及凝胶形成浓度的影响, 结果发现, 亲水嵌段越短, 越有利于长椭球状胶束的形成, 而临界凝胶浓度随着亲水嵌段PEO长度的增加而降低.     

组装-聚合法制备聚苯乙烯-聚丙烯酸胶束和凝胶

通过苯乙烯和丙烯酸单体的预组装再聚合的制备方法,在不改变共聚物浓度的前提下制备了共聚物胶束溶液和凝胶,探讨了引发剂(偶氮二异丁腈)浓度对生成的共聚物的聚集体结构以及分子结构的影响.利用核磁共振氢谱、扫描电子显微镜和透射电子显微镜等表征了共聚物的分子结构和聚集行为,此外,借助耗散粒子动力学方法模拟了该体系,辅助实验阐明了不同引发剂浓度下生成的共聚物聚集体结构及相对应的共聚物分子结构,在此基础上,利用动态机械热分析和流变学的表征技术,研究了共聚物胶束溶液和凝胶的流变特性.结果表明,在单体浓度不变的情况下,高引发剂浓度时该体系趋于形成平均嵌段长度较长的两嵌段共聚物,生成稳定的胶束溶液,而低引发剂浓度时趋于形成交替共聚物,得到物理凝胶,耗散粒子动力学模拟得到了与实验一致的结果.流变学表征发现胶束体系和凝胶体系均呈现剪切变稀行为,并确定了凝胶体系的凝胶点及恢复性.     

线球状银颗粒的液相合成及其机理研究

本文在三嵌段共聚物Pluronic F127/十二烷基硫酸钠(SDS)混合表面活性剂体系中制备了直径为 3～4 μm的线球状 Ag 颗粒。实验发现随着体系中SDS浓度的增加,组成Ag微球的亚单元从椭球状经由棒状变成了纳米线。动态光散射数据表明随着SDS的加入,F127胶束被F127/SDS混合胶束所取代,且混合胶束尺寸随着SDS浓度的变化而变化。实验表明SDS的烷基链段与F127的憎水PPO链段的相互吸引作用,以及SDS亲水基团之间的静电排斥作用将影响产物的最终结构。     

十二烷基硫酸钠对聚乙烯醇亚浓水溶液流变行为的影响

表面活性剂会影响聚乙烯醇(PVA)分子间及分子内氢键形成,进而改变其水溶液的流变响应.本文在确定十二烷基硫酸钠(SDS)在PVA亚浓水溶液中的临界聚集浓度(CAC)和临界胶束浓度(CMCP)基础上,考察了SDS对PVA亚浓溶液(10 wt%)流变行为的影响.研究发现,不同浓度SDScsur对PVA水溶液稳态流变行为的影响差异较大:(1)当csur CMCP,随着csur增加,胶束起物理交联点作用,ηa增大,复合溶液的动态储能模量亦显著增大.加入SDS后,PVA体系内结合水的数目降低,但当csur> CMC后,结合水的数目几乎不变,黏流活化能也表现出相近的变化规律.与稀溶液相比,SDS对PVA亚浓溶液的降黏幅度较大.     

17R4/F127混合水溶液的凝胶结构

结合流变学频率扫描和同步辐射小角X射线散射(SAXS), 研究了17R4(PO₁₄-EO₂₄-PO₁₄)含量和温度对17R4/F127(EO₉₉-PO₆₅-EO₉₉)混合水溶液凝胶结构的影响. 结果表明, 溶胶、 软凝胶和硬凝胶分别对应无序结构、 无序与立方相共存结构以及立方相结构. 对于F127水溶液体系, 可以将F127形成的胶束看作硬球, 随着温度的升高, 胶束的硬球半径和胶束中F127链的聚集数随之减小, 这是因为17R4在较低温度下很难形成胶束, 当温度升高时, 17R4链参与胶束的形成, 从而使胶束数目增加, 因此每个胶束中的F127链数也随之减小. 当17R4含量较高时, 胶束外壳中F127部分的PEO链段数随着温度升高而减小, 胶束外壳变得更软, 因此, 当17R4/F127摩尔比为2: 1时, 混合溶液在高温下呈现面心立方(fcc)到体心立方(bcc)的结构转变.     

表面活性剂对纤维素接枝共聚物溶液粘度性质的影响

研究了阴离子十二烷基硫酸钠(SDS)、阳离子十六烷基三甲基溴化铵(CTAB)和非离子聚乙二醇辛基苯基醚(OP)等三种不同类型的表面活性剂对疏水化水溶性两性纤维素接枝共聚物(CGAO)溶液粘度性质的影响.结果表明,在SDS和OP的临界胶束浓度(cmc)附近，CGAO溶液粘度最大，SDS引起CGAO粘度的变化大于OP；即使在CTAB的cmc附近，随着CTAB浓度的增加，CGAO的粘度一直呈下降趋势；非疏水改性的纤维素接枝共聚物的溶液粘度随SDS或CTAB浓度的增加而下降，但几乎不随OP浓度的增大而变化.此外，通过凝胶渗透色谱法测得的保留时间证实了SDS、CTAB和OP与CGAO之间的疏水缔合作用.     

两相催化1—十二烯氢甲酰化反应中混合胶束的作用研究

研究了RhCl(CO)(TPPTS)2催化-1-十二烯氢甲酰化反应中,十六烷基三甲基溴化铵（CTAB）与十二烷基硫酸钠（SDS）形成的混合胶束对反应的促进作用。研究结果表明,随SDS在混合表面活剂溶液中比例的增大,1-十二烯生成醛的转华率先增大后又降低,并从混合胶束的临界胶束浓度及混合胶束对底物增溶作用的变化对这一结果进行了讨论。     

含叶酸功能端基Pluronic F127的合成及其在水中的形态

通过一系列反应将三嵌段共聚物Pluronic F127的端羟基转变为氨基。利用氨基化F127大单体,最终成功的将生物活性大分子叶酸接到了F127端基上(F127-Folate) 作为靶向配体。利用1H-NMR对嵌段共聚物的结构进行了表征。用透析法制备胶束溶液,利用TEM研究了F127-Folate在水溶液中的自组装形态,结果表明F127-Folate正在水溶液中自组装形成纳米胶束。     

嵌段结构对两亲嵌段共聚物水溶液行为的影响

在合成了二种具有相同组成不同嵌段结构排布的共聚物基础上对它们溶液的物理化学行为用荧光探针的方法进行了研究，结果表明：由于结构排布的不同其物理化学行为有着较大的差异，三嵌段结构的共聚物较二嵌段者更易于形成胶束体系，而二嵌段共聚物则易于发生凝胶化，对上述结果进行讨论和解释．     

淋洗剂凝胶渗透色谱研究环氧乙烷-环氧丙烷-环氧乙烷三嵌段共聚物胶束溶液对苯乙醇的增溶作用

提出了用凝胶渗透色谱研究胶束溶液增溶作用的新方法，并给出了环氧乙烷-环氧丙烷-环氧乙烷三嵌段共聚物F127胶束溶液苯乙醇的实验结果。实验方便快捷，原理直观明了。在获得增溶作用参数的同时还能得到胶束-自由链平衡的重要信息。     

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.     

甲基丙烯酸3-磺酸钾丙酯-苯乙烯共聚物与N,N,N-三甲基十六烷基溴化铵相互作用研究

两亲分子由于具有自组装性质,如表面活性剂分子自组装形成胶束,囊泡,天然的磷脂分子自组装形成脂质体,继而参于生物膜的形成,这是大家所熟悉的．高分子两亲分子尤其是两亲性两嵌段高分子具有自组装性质,并形成规整性好的聚集体［１～３］．聚电介质 表面活性剂体系...     

Mechanisms of micellization and rheology of PEO-PPO-PEO triblock copolymers with various architectures

Micelle formation was followed by micro-DSC and rheology for aqueous solutions of two copolymers of PEO-PPO-PEO, the Pluronic F127 (from BASF) and the EG56 (from PolymerExpert), a branched copolymer built with three chains of F127 type. It is shown that micellization is endothermic and that, for both polymers, the enthalpy of formation/melting is proportional to total concentration. The rheology of the solutions was carefully analyzed, before gelation for F127, and it reveals firstly the progressive changes of solubility of the unimers (decease of relative solution viscosity), followed by micelle formation over a 10 degrees C range. In this range, the micelle concentration dependence on temperature was deduced from enthalpy measurements and the corresponding volume fractions were derived. Viscosity was interpreted within the framework of well-known theories for hard sphere suspensions (Krieger-Dougherty or Quemada) based on an analogy between micelles and nanosized hairy grain suspensions. The gel state is achieved due to formation of the colloidal crystal. For EG56, the rheology is quite different; as the aggregation increases with temperature, a progression is observed from Newtonian to visco-elastic liquid. The characteristic frequency, defined by the relation G(') = G('), for EG56 varies with temperature and the corresponding times increase by two orders of magnitude according to an Arrhenius law. The frequency dependence of G(') and G(') at different temperatures can be superposed with a horizontal shift factor and a small amplitude adjustment. There is no elastic solid formation in this case. The "gelation" of these two copolymers is compared to the physical gelation of cold-set gels (gelatin).     

Effect of SDS on the self-assembly behavior of the PEO-PPO-PEO triblock copolymer (EO)20(PO)70(EO)20

The mixed micellar system comprising the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-based triblock copolymer (EO)(20)(PO)(70)(EO)(20) (P123) and the anionic surfactant sodium dodecyl sulfate (SDS) has been investigated in aqueous media by small-angle neutron scattering (SANS) and viscosity measurements. The aggregation number of the copolymer in the micelles decreases upon addition of SDS, but a simultaneous enhancement in the degree of micellar hydration leads to a significant increase in the micellar volume fraction at a fixed copolymer concentration. This enhancement in the micellar hydration leads to a marked increase in the stability of the micellar gel phase until it is destroyed at very high SDS concentration. Mixed micellar systems with low and intermediate SDS concentrations form the micellar gel phase in much wider temperature and copolymer concentration ranges than the pure copolymer micellar solution. A comparison of the observed results with those for the copolymers (EO)(26)(PO)(40)(EO)(26) (P85) and (EO)(99)(PO)(70)(EO)(99) (F127) suggests that the composition of the copolymers plays a significant role in determining the influence of SDS on the gelation characteristics of the aqueous copolymer solutions. Copolymers with high PO/EO ratios show an enhancement in the stability of the gel phase, whereas copolymers with low PO/EO ratios show a deterioration of the same in the presence of SDS.     

Microstructure transition of hydrophilic modified ibuprofen and Pluronic copolymer F127 complexes

The effect of the aggregation state of Pluronic copolymer (PEO₁₀₀–PPO₆₅–PEO₁₀₀, F127) and the concentration of hydrophilic modified ibuprofen (Ibuprofen–PEG800, IP800) on the interaction between F127 and IP800 was systematically investigated by nuclear magnetic resonance, dynamic light scatter (DLS), surface tension, and freeze-fractured transmission electron microscopy. In the solution of F127 unimers (5 °C), F127 unimers tended to wrap around IP800 micelles, and the binding model of F127 unimers to IP800 micelles transferred from wrapping around to partly threading through with increasing IP800 concentration. The latter binding model was straightly confirmed by nuclear Overhauser enhancement spectroscopy. As the aggregation state of F127 is in the beginning of the micellization (20 °C), the addition of IP800 significantly promoted the micellization of F127 to form the F127/IP800 complex with F127 micelles as the skeleton called the F127–micelle complex. The sudden decrease of the size obtained from DLS stemmed from the disruption of the F127–micelle complex and accompanying rehydration of PPO which is weaker compared with refs. The amount of IP800 to disintegrate the F127–micelle complex increased in the F127–micelle-dominated solution (40 °C) compared to that at 20 °C.     

Formation and microstructure transition of F127/TX-100 complex

Formation and structure transition of the complex composed of triblock copolymer F127 and nonionic surfactant TX-100 have been investigated by 1H NMR spectroscopy, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). Three TX-100 concentration regions are identified, within which TX-100/20 mg/mL F127 complex undergoes different temperature-induced structure transitions. In low concentration region (< 9.42 mM), F127 single molecular species (unimers) wrap around TX-100 micelles forming F127/TX-100 complex with TX-100 micelle as the skeleton at a lower temperature (5 degrees C), and the skeleton transfers to F127 micelle at higher temperature (40 degrees C); in intermediate TX-100 concentration region (9.42-94.85 mM), the skeleton of F127/TX-100 complex transfers from TX-100 micelle successively into F127 micelle and TX-100 micelle again upon heating. The interaction of F127 with TX-100 is saturated in high TX-100 concentration region (> 157.57 mM), and free TX-100 micelles coexist with larger clusters of F127/TX-100 complexes. In addition, TX-100-induced F127/TX-100 complex formation and structure transition are also investigated at constant temperatures. The results show that within 5-10 degrees C, F127 unimers mainly adsorb on the surface of TX-100 micelles just like normal water soluble polymers; in the temperature region of 15-25 degrees C, TX-100 micelles prompts F127 micelle formation. Within 30-40 degrees C, TX-100 inserts into F127 micelles leading to the breakdown of F127 aggregates at higher TX-100 concentrations, and the obtained unimers thread through TX-100 micelles forming complex with TX-100 micelle as skeleton.     

Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone), on the gelation of aqueous micellar solutions of Pluronic copolymer F127

The micellization of F127 (E(98)P(67)E(98)) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (r(h,app)) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G(max)(')) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.     

Effects of a PPO-PEO-PPO triblock copolymer on micellization and gelation of a PEO-PPO-PEO triblock copolymer in aqueous solution

The effects of a PPO-PEO-PPO triblock copolymer (25R4, PO(19)-EO(33)-PO(19)) on thermoreversible micellization and gelation properties of a PEO-PPO-PEO triblock copolymer (F108, EO(133)-PO(50)-EO(133)) in water were studied by means of micro-DSC and rheology. A complete, mirror-image like thermoreversible behavior has been observed for all of the samples with various molar ratios of 25R4 to F108. At a given concentration of F108, the addition of 25R4 results in the salt-out like effect on the primary micellization of F108; that is, the critical micellization temperature (CMT) of F108 shifts to lower temperatures with increasing the content of 25R4. The enthalpy changes for micellization are a linear function of the 25R4/F108 molar ratio at a fixed F108 concentration. Beyond the primary peak for the micellization of F108, a secondary peak or shoulder is observed in the DSC curves for the samples with the higher 25R4/F108 molar ratios, due to the formation of the hydrophobic aggregates from both the PPO blocks of F108 and those (i.e., PPO blocks) of 25R4. Furthermore, as an example, the dynamic viscoelastic properties of 18 wt % F108 solutions with various contents of 25R4 have been examined. It is found that, when the 25R4/F108 molar ratio < or =1, 25R4 does not affect the gelation of F108 notably. When the ratio is greater than 1, however, the formation of the 25R4-bridged micellar aggregates delays the gelation of F108 significantly. A schematic model has been proposed to explain the mechanism for the 25R4-influenced micellization and gelation of F108.     

树枝聚醚改性聚丙烯酰胺和阴离子表面活性剂的缔合行为

采用粘度法、荧光探针技术和^1H NMR驰豫和自扩散方法，研究了树枝聚醚疏 水改性丙烯酰胺共聚物(PDAM)和十二烷基硫酸钠(SDS)在水溶液中的相互作用．这 种共聚物含有少量的树枝聚醚，具有疏水性，容易和SDS发生相互作用，在表面活 性剂浓度远低于临界胶束浓度(cmc)的情况下，生成混合胶束状聚集体．它们的缔 合行为和溶液性质明显地取决于表面活性剂的浓度，随着聚合物溶液中加入SDS， 溶液粘度发生急剧变化，并在较低的表面活性剂浓度处出现很大的最高点．荧光和 ^1H NMR测定结果表明，这是由于在不同SDS浓度范围内，PDAM/SDS形成的聚集体结 构不同的缘故．     

Effect of pharmaceuticals on thermoreversible gelation of PEO-PPO-PEO copolymers

Pluronic F127, a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), has generated considerable interest as a drug delivery vehicle due to its ability to gel at physiological temperatures. This work examines the gelation behavior of Pluronic F127 in the presence of a series of hydrophobic pharmaceuticals, to determine whether there is any correlation between gelation and physicochemical parameters of drug solutes. The study includes the local anesthetics dibucaine, lidocaine, and tetracaine; the pharmaceutical additives methyl paraben, ethyl paraben, and propyl paraben; the anti-cancer agents paclitaxel and baccatin III; and the anti-inflammatory agent sulindac. The results indicate that the presence of local anesthetics and pharmaceutical additives allows F127 solutions to form gels at lower copolymer concentrations; local anesthetics and pharmaceutical additives also shift gelation down to a lower gelation temperature. This behavior is strongly dependent on drug solubility; poorly soluble drugs (paclitaxel, baccatin III, sulindac) do not change the lower gelation temperature or minimum F127 concentration for gelation. An equation relating the decrease in gelation temperature to drug solubility is presented, and the equation fits the data well. The results have significant positive implications on the toxicity and economic issues related to use of Pluronic F127 in drug delivery.