Formation and properties of reverse micellar cubic liquid crystals and derived emulsions.
Formation and properties of reverse micellar cubic liquid crystals and derived emulsions.
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DOI：
10.1021/la701722f
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
C. Rodríguez‐Abreu;L. Shrestha;D. Varade;K. Aramaki;A. Maestro;A. L. Quintela;C. Solans
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文献类型：
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作者：
C. Rodríguez‐Abreu;L. Shrestha;D. Varade;K. Aramaki;A. Maestro;A. L. Quintela;C. Solans
用小角X射线散射（SAXS）、流变仪和差示扫描量热法（DSC）研究了两亲嵌段共聚物/水/油体系中的反胶束立方（I2）液晶和相邻胶束相的结构。在向共聚物/油混合物中加入水后，形成球形胶束并在尺寸上生长，直到发生无序-有序转变，这与粘度和剪切模量的突然增加有关。该转变是由球形胶束堆积成Fd 3 m立方晶格驱动的。单相I2液晶显示凝胶状行为和弹性模量高于104 Pa，由振荡测量确定。进一步加入水诱导相分离，发现在两相区可以制备具有高内相比且由I2液晶稳定的反相油包水乳液。与液-液乳液相反，弹性模量和粘度都随着分散水的分数而降低，这是由于样品中结晶分数的降低，尽管反相乳液即使在分散相的高体积分数下也保持凝胶状。温度诱导的有序-无序转变可以通过量热法和流变法检测。在加热I2液晶时，检测到与小焓值相关的两个热事件：一个吸热，与液晶的“熔化”相关，另一个放热，归因于相分离。液晶的熔化与粘度和剪切模量的突然下降相关联。结果是相关的理解形成的反相为基础的反相乳液，并为他们的应用程序作为模板合成的结构材料。
The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 104 Pa, as determined by oscillatory measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase. A temperature induced order-disorder transition can be detected by calorimetry and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials.