Langmuir 1992,8, 1054-1059
1054
Interaction of Poly(oxyethy1ene glycol) with Cyclohexane-Pentanol-Sodium Dodecyl Sulfate Water-in-Oil Microemulsions Panagiotis Lianos,*-tSotirios Modes,t George Staikos,: and Wyn Brown8 School of Engineering, Physics Section, University of Patras, 26000 Patras, Greece, Department of Chemical Engineering, University of Patras, 26000 Patras, Greece, and Department of Physical Chemistry, University of Uppsala, 75121 Uppsala, Sweden Received August 19, 1991. I n Final Form: December 23, 1991 The interaction of poly(oxyethy1ene glycol) (MW 6000) with cyclohexaneil-pentanol/sodiumdodecyl sulfate microemulsions was studied with dynamic light scattering and luminescence probing techniques. Some conductivity measurements have also been made. Particular weight has been given to luminescence. We have chosen to analyze luminescence decay profiles by using models obtained from the theory of random walk in fractal domains, in order to deal with percolation phenomena present in the above system and to underline new information obtained by fractal models. Ru(bpy),2+has been used as the lumophore and Fe(CN)e3-as the quencher. It was found that the polymer induces a structural reorganization of the dispersed phase so that the aggregates grow in size. The geometry of the dispersed phase becomes more restricted in the presence of polymer and the quenching efficiency decreases. The electric conductivity undergoes a limited decrease.
Introduction The effect of water-soluble polymers on surfactant aggregation is an interesting problem which has occupied several laboratories ~ o r l d w i d e . ~However, -~~ most work has been carried out in the aqueous phase, while the interaction between water-in-oil microemulsion and watersoluble polymers was studied mainly in the domain of gel formation with the use of gelating agents.16-19 However, to better understand such systems, it is necessary to study, among other things, the interactions between microemulsion droplets and simple polymers. For this reason, we are investigating the interaction between a model quaternary water-in-oil microemulsion, consisting of cyclohexane, 1-pentanol, sodium dodecyl sulfate, and water, and poly(oxyethy1eneglycol) (MW 6000),which is expected to be solubilized almost entirely in the dispersed phase. The interaction is studied by dynamic light scattering, conductivity, and luminescence probing. Particular weight +
School of Engineering, Physics Section, University of Patras.
* Department of Chemical Engineering, University of Patras. Department of Physical Chemistry, University of Uppsala.
(1) Zana, R.; Lianos, P.; Lang, J. J. Phys. Chem. 1985, 89, 41. (2) Tondre, C. J . Phys. Chem. 1985, 89, 5101. (3) Binana-Limbele, W.; Zana, R. Colloids Surf. 1986, 21, 483. (4) Deh-ying, C.; Thomas, J. K. J . A m . Chem. SOC.1986, 108, 6270. (5) Brackman, J.; Engberts, J. B. F. N. Langmuir 1991, 7 , 46. (6) Balms, A,; Hu, J. Y. Langmuir 1989, 5, 1230. (7) Winnik, F. M. Langmuir 1990, 6, 522. (8) Ju, Y.-Z.; Zhao, C.-L.; Winnik, M. A,; Sundararajan, P. R. Langmuir 1990, 6 , 880. (9) Carlsson. A.; Lindman. B.: Watanabe. T.: Shirahama, K. Lonamuir 1989, 5 , 1250. (10) Takisawa, N.; Brown, P.; Bloor, D.; Hall, D. G.;Wyn-Jones, E. J . Chem. SOC.,Foradoy T r a m . 1 1989,85, 2099. (11)Esumi, K.; Meguro, K. J . Colloid Interfoce Sci. 1989, 129, 217. (12) Chandar, P.; Somasumdaran. P.: Turro. N. J. Macromolecules 1988, 21, 950.
is given to the last method which is presently applied using a new model obtained from the theory of random walk in fractal domains. Luminescence quenching in water-in-oil microemulsions, which represents the bimolecular reaction A B products ([AI
