Bandula Rodica, Vasilescu Marilena, Lemmetyinen Helge
Romanian Academy, I.G. Murgulescu Institute of Physical Chemistry, Splaiul Independentei 202, 060021 Bucharest, Romania.
J Colloid Interface Sci. 2005 Jul 15;287(2):671-7. doi: 10.1016/j.jcis.2005.02.012.
The micropolarities of the reverse micelle (RM) interior of nonionic poly(ethylene oxide) surfactants of the alkyl ether type (poly(ethylene oxide)[4] lauryl ether (C12E4, Brij 30)), alkyl-aryl ethers (poly(ethylene oxide)[4] nonylphenyl ether (C9PhiE4), poly(ethylene oxide)[5] nonylphenyl ether (C9PhiE5), and poly(ethylene oxide)[5] octylphenyl ether (C8PhiE5)), and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers (Pluronics P123, F127) were investigated as a function of the water content by applying the absorption probe technique, using 4-nitropyridine-N-oxide (NP) as a probe. The change in the micellar aggregate micropolarity in different solvents (cyclohexane, decane, n-butanol, and n-butyl acetate) at various water contents has been investigated. The research was focused on the determination of the effects of surfactant structure and solvent type on the hydration degrees of the PEO chains in the region at the core limit, where the NP probe was located. All results regarding the polarities in RM and PEO/water calibration mixtures have been expressed in terms of Kosower's Z values, using the linear dependence of E(NP) on Kosower's Z. The PPO/butanol mixtures have also been used for RM in butanol as a reference system. The data revealed that local polarity in RM is dependent on the surfactant type, block copolymer composition, solvent nature, and water content. At the same water content, the results clearly indicate a lower hydration degree of triblock copolymers, as compared to the surfactants of the alkyl ether and alkyl-aryl ether type, but for P123 and F127 Pluronics in n-butanol the hydration is higher owing to the behavior of butanol as cosurfactant and to its hydration.
通过应用吸收探针技术，以4-硝基吡啶-N-氧化物（NP）作为探针，研究了烷基醚型（聚环氧乙烷[4]月桂基醚（C12E4，Brij 30））、烷基芳基醚（聚环氧乙烷[4]壬基苯基醚（C9PhiE4）、聚环氧乙烷[5]壬基苯基醚（C9PhiE5）和聚环氧乙烷[5]辛基苯基醚（C8PhiE5））以及聚环氧乙烷-聚环氧丙烷-聚环氧乙烷（PEO-PPO-PEO）三嵌段共聚物（普朗尼克P123、F127）的反胶束（RM）内部的微极性随水含量的变化。研究了在不同水含量下，不同溶剂（环己烷、癸烷、正丁醇和乙酸正丁酯）中胶束聚集体微极性的变化。该研究的重点是确定表面活性剂结构和溶剂类型对NP探针所在的核心极限区域中PEO链水合度的影响。关于RM和PEO/水校准混合物中极性的所有结果均根据Kosower的Z值表示，利用E(NP)对Kosower的Z的线性依赖性。PPO/丁醇混合物也被用作丁醇中RM的参考体系。数据表明，RM中的局部极性取决于表面活性剂类型、嵌段共聚物组成、溶剂性质和水含量。在相同水含量下，结果清楚地表明，与烷基醚和烷基芳基醚型表面活性剂相比，三嵌段共聚物的水合度较低，但对于正丁醇中的P123和F127普朗尼克，由于丁醇作为助表面活性剂的行为及其水合作用，水合度较高。
