Surface activity—thermodynamic properties and light scattering studies for some novel aliphatic polyester surfactants |
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Authors: | R A El‐Ghazawy R Abdel Raheem A M Al‐Sabagh |
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Institution: | 1. Egyptian Petroleum Research Inst., Nasr City, Cairo, 11727, Egypt;2. Physikalische Chemie I., Universitat Bayreuth, Universitat str. 30, D‐95445 Bayreuth, Germany;3. Egyptian Petroleum Research Inst., Nasr City, Cairo, 11727, EgyptEgyptian Petroleum Research Inst., Nasr City, Cairo, 11727, Egypt. |
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Abstract: | The preparation of 12 new polyester surfactants based on aliphatic amines and different ethylene oxide content is described. These surfactants were characterized by determining their molecular weights and polydispersity by gel permeation chromatography (GPC) and nitrogen content. Drop volume tensiometry (DVT) was used to measure the surface tension at 25, 35, 45 and 55°C. The surface tension isotherms were used to determine critical micelle concentration (CMC), maximum Gibb's adsorption (Γmax), minimum area per molecule (Amin), the effectiveness of surface tension reduction (πcmc) and the efficiency (pC20). The thermodynamic parameters of micellization (ΔGmic, ΔHmic, ΔSmic) and of adsorption (ΔGad, ΔHad, ΔSad) were calculated and the data showed that these surfactants favor micellization to adsorption. The static scattered light intensity measurements provide the calculation of the molecular weight of micelle and the aggregation number (N°), while the dynamic light scattering provide the hydrodynamic radius of micelle (RH) and the diffusion coefficient at different surfactant concentrations. The hydrodynamic radius of micelle (RH) at different surfactant concentrations could be used also to determine the CMC giving results that are comparable to those obtained by surface tension measurements. All the data are discussed regarding the chemical structure of the polymeric surfactants. Copyright © 2004 John Wiley & Sons, Ltd. |
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Keywords: | surfactants polyesters aggregation number light scattering thermodynamics |
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