title: Mass-fractal clustering and power-law decay of cluster size in 1-propanol aqueous solution.
abstract: Mesoscale structure of 1-propanol aqueous solutions with propanol mole fraction xp ranging from 0.1 to 0.33 has been studied by means of small angle neutron scattering (SANS) and large-scale reverse Monte Carlo (RMC) technique. Analysis of the SANS intensities in terms of a fractal model shows that the fractal dimension df of mesoscale structure of the solution is about 1.8-1.9 for water-rich solution and about 1.5 for propanol-rich solution. Percolation analysis on the RMC results reveals that the water molecules and the propanol molecules cluster, respectively, as a mass fractal, the dimension dM of which is about 2.3-2.5 for both clusters for water-rich solution. Furthermore, the distribution of the cluster size is expressed by a simple power law with an exponent tau of about 1.35-1.5 for the propanol clusters and 1.05-1.2 for the water clusters. These results imply that the current solution is characterized by polydisperse mass fractals. In fact, a theoretical relation for polydisperse system of mass fractals, df = dM(2-tau), holds well in the current solution. The characteristic change in df from 1.8-1.9 to 1.5 described above is attributed to the crossover between the water-rich regime and the propanol-rich regime. Most of the water molecules and the propanol molecules are located on the interface between clusters, and the water molecules form thin layers of about 10 A thick irrespective of 1-propanol content studied.
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University, Niigata 950-2181, Japan. misawa@chem.sc.niigata-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Misawa
authors.forename: I
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authors.lastname: Dairoku
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authors.initials: A
authors.lastname: Honma
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authors.lastname: Yamada
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authors.lastname: Sato
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authors.lastname: Maruyama
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authors.lastname: Mori
authors.forename: S
authors.initials: S
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Otomo