Effect of inorganic salts on the aggregation behavior of branched block polyether at air/water and n -heptane/water inte
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ORIGINAL CONTRIBUTION
Effect of inorganic salts on the aggregation behavior of branched block polyether at air/water and n-heptane/ water interfaces Xueru Zhai & Guiying Xu & Yijian Chen & Teng Liu & Juan Zhang & Jing Yuan & Yebang Tan & Jian Zhang
Received: 3 January 2013 / Revised: 9 June 2013 / Accepted: 13 June 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The effect of inorganic salts (CaCl2, MgCl2, NaCl, NaI and NaSCN) on the aggregation behavior of a synthesized polyether with seven poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) (PEO-PPO-PEO) arms attached to a tetraethylenepentamine core (simplified AE73) at air/water and n-heptane/water interfaces has been investigated by interfacial tension and oscillating bubble methods. The additions of NaCl, CaCl2, and MgCl2 may facilitate the micellization of AE73 and increase its maximum interfacial excess concentration (Γmax) due to the “salting out” effect, while NaSCN induces opposite effect and NaI exerts little influence. The adsorption kinetics of AE73 is controlled not only by the diffusion between the bulk solution and the interfacial layer but also by the energetic and steric barriers generated by the already adsorbed molecules. The adsorption relaxation time of AE73 is reduced with the addition of salts and this phenomenon is more prominent at the n-heptane/water interface. The “salting in” ions decrease the dilational modulus of AE73 while the “salting out” ions induce an opposite effect. The mechanisms of the interaction between inorganic ions and the polyether were discussed; the difference in aggregation behavior between linear and branched block polyethers were also compared.
Electronic supplementary material The online version of this article (doi:10.1007/s00396-013-3013-y) contains supplementary material, which is available to authorized users. X. Zhai : G. Xu (*) : Y. Chen : T. Liu : J. Zhang : J. Yuan : Y. Tan Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, People’s Republic of China e-mail: [email protected] J. Zhang Technology Research Dept, CNOOC Research Center, State Key Laboratory of Offshore Oil Exploitation, Beijing 100027, People’s Republic of China
Keywords Branched PEO-PPO-PEO block polyether . Inorganic salt . Interfacial tension . Dilational viscoelasticity
Introduction The poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) (PEO-PPO-PEO) copolymers have been widely used in many fields for their low-cost, low-toxicity and biodegradable properties [1–4]. There are two families according to their structures: the linear PEO-PPO-PEO polyethers and the branched ones. The behaviors of the linear polyethers both in bulk solution and at interfaces have been extensively explored, including many influencing factors such as the molecular structure and concentration of polyether, temperature, pH and additives [4–9]. However, the polyethers with branched structure have been rarely studied, although they have been proved to have
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