Temperature-Dependent Phase Behavior of Polyelectrolyte-Mixed Micelle Systems

详细信息    查看全文

• 作者：Anil Kumar ; Paul L. Dubin ; Michael J. Hernon ; Yajuan Li ; Werner Jaeger
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：July 26, 2007
• 年：2007
• 卷：111
• 期：29
• 页码：8468 - 8476
• 全文大小：268K
• 年卷期：v.111,no.29(July 26, 2007)
• ISSN：1520-5207

文摘

The effect of temperature on the phase behavior of a polycation-anionic/nonionic mixed micelle system,poly(dimethyldiallylammonium chloride)-sodium dodecylsulfate/Triton X-100, was studied over a wide rangeof surfactant compositions, ionic strengths, and polycation molecular weights using turbidimetry and dynamiclight scattering. Soluble complexes become biphasic upon heating through either liquid-liquid (coacervation)or liquid-solid (precipitation) separation. The biphasic boundary comprises two regions: a coacervate domainexhibiting a lower critical solution temperature and a second superimposed domain in which either solids orvery dense and viscous fluids are formed upon heating. The position of the first region is symmetricallycentered around conditions corresponding to charge neutralization of complexes and their aggregates at incipientphase separation. The second region, observed at high micelle charge, corresponds to the collapse of polycationonto micelle surfaces and expulsion of counterions and can produce either dense coacervate or precipitate.The two regions exhibit different dependences on ionic strength, polyelectrolyte molecular weight, andconcentration, from which inferences about the mechanisms of phase separation may be drawn. Preliminaryobservations of the dense liquid phases isolated after coacervation disclose a number of interesting opticaland rheological properties, possibly arising from shear-induced phase separation.