{"product_id":"non-ionic-binary-surfactant-systems-and-microemulsions-as-model-systems-for-thermal-diffusion-studies-von-sascha-datta","title":"Non-Ionic Binary Surfactant Systems and Microemulsions as Model Systems for Thermal Diffusion Studies","description":"\u003cp\u003eThermal diffusion (or the Soret effect) describes the diffusion of matter in the presence of a\u003c\/p\u003e\u003cp\u003etemperature gradient. Although this process is studied and applied since more than 100 years the\u003c\/p\u003e\u003cp\u003eunderlying molecular mechanism in liquids is still far from being understood. Colloidal\u003c\/p\u003e\u003cp\u003edispersions are versatile model systems to study the thermal diffusion behavior of large particles\u003c\/p\u003e\u003cp\u003ein a solvent. However, the synthesis of colloidal particles with identical morphology is a\u003c\/p\u003e\u003cp\u003ecomplex task. On the other hand aqueous surfactant solutions and microemulsions are promising\u003c\/p\u003e\u003cp\u003esystems to study the Soret effect. Compared to colloidal particles the aggregates form\u003c\/p\u003e\u003cp\u003espontaneously and do not require any additional stabilisation. Furthermore the radius and the\u003c\/p\u003e\u003cp\u003eshape of the diffusing aggregates, as well as their interfacial tension can be systematically\u003c\/p\u003e\u003cp\u003eadjusted via the variation of the composition and temperature. In order to address some\u003c\/p\u003e\u003cp\u003eimportant aspects of the thermal diffusion behavior three different types of self-assembled\u003c\/p\u003e\u003cp\u003esurfactant systems were formulated and systematically studied: (i) At first the role of the ionic\u003c\/p\u003e\u003cp\u003edye Basantol® Yellow 215, which causes an unexpected two-mode signal in the classical\u003c\/p\u003e\u003cp\u003eThermal Diffusion Forced Rayleigh Scattering (TDFRS) experiment [Ning et al. Progr Colloid\u003c\/p\u003e\u003cp\u003ePolym Sci (2006) 133: 111¿115], is examined using the system H2O ¿ C12E6. Systematic phase\u003c\/p\u003e\u003cp\u003ebehavior studies and small angle neutron scattering experiments (SANS) proved that the dye is\u003c\/p\u003e\u003cp\u003eincorporated into the aggregates like an ionic co-surfactant, influencing not only the thermal\u003c\/p\u003e\u003cp\u003ediffusion behavior but also the overall properties of the systems. These results strongly suggest\u003c\/p\u003e\u003cp\u003ethat one should refrain from the use of surface-active dyes in TDFRS experiments on\u003c\/p\u003e\u003cp\u003eself-assembled systems. (ii) To study the dependence of the Soret coefficient ST on the radius of\u003c\/p\u003e\u003cp\u003ethe aggregates and the slope of the interfacial tension, both being controversially discussed in the\u003c\/p\u003e\u003cp\u003eliterature, different microemulsions of the type H2O ¿ C12E5 ¿n-alkane were formulated that\u003c\/p\u003e\u003cp\u003eallow for an isothermal study of these dependencies. Correlating the results of the systematic\u003c\/p\u003e\u003cp\u003eSANS and interfacial tension measurements with the Soret coefficient ST it was found that within\u003c\/p\u003e\u003cp\u003ethe measurement range ST depends almost linearly on the droplet radius, the slope of the\u003c\/p\u003e\u003cp\u003einterfacial tension as well as on the product of both quantities. (iii) In the last part systematic\u003c\/p\u003e\u003cp\u003esurface tension and TDFRS measurements were performed in binary aqueous n-alkyl glucoside\u003c\/p\u003e\u003cp\u003e(CiGj) solutions to study the thermal diffusion behavior around the critical micelle concentration\u003c\/p\u003e\u003cp\u003e(cmc). The obtained results clearly show that the Soret coefficient exhibits an abrupt change at\u003c\/p\u003e\u003cp\u003ethe cmc. To sum up, this work shows that aqueous surfactant systems and microemulsions are\u003c\/p\u003e\u003cp\u003eeminently suited to elucidate some of the underlying molecular mechanism of the Soret effect.\u003c\/p\u003e\u003cdiv class=\"aw-variant-hidden-subtitle-div\" id=\"aw-variant-subtitle-9783869559711\"\u003e\u003ch3\u003e\u003c\/h3\u003e\u003c\/div\u003e","brand":"Autorenwelt Shop","offers":[{"title":"Softcover - 9783869559711","offer_id":39531883561053,"sku":"9783869559711","price":34.3,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0940\/0622\/files\/8f1ad8ad-9a73-4e67-90f6-46ade93d1f32.jpg?v=1778647421","url":"https:\/\/shop.autorenwelt.de\/en\/products\/non-ionic-binary-surfactant-systems-and-microemulsions-as-model-systems-for-thermal-diffusion-studies-von-sascha-datta","provider":"Autorenwelt Shop","version":"1.0","type":"link"}