Interactions of quaternary ammonium salt-type gemini surfactants with

Tomokazu Yoshimura,∗ Yukiko Nagata, and Kunio Esumi
Department of Applied Chemistry and Institute of Colloid and Interface Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan Received 22 September 2003; accepted 4 March 2004 Available online 10 April 2004
T. Yoshimura et al. / Journal of Colloid and Interface Science 275 (2004) 618–622
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2.3. Measurements The surface tension of aqueous solutions of surfactants/PSS mixed systems was measured with a Krüss K100 tensiometer by using the Wilhelmy plate technique. Steadystate fluorescence spectra of pyrene in the mixed systems were obtained using a Hitachi 650-10S spectrophotometer in the range 360–400 nm at an excitation wavelength of 335 nm, where the concentration of pyrene was 1 × 10−5 mol dm−3 . Dynamic light scattering was also performed with a DLS-7000, Otsuka Electronics Company, Ltd., spectrophotometer using an argon laser of 488 nm. All solutions were filtered with a 0.2-µm filter of mixed cellulose acetate. All measurements were carried out at 25 ◦ C.
E-mail address: yoshimura@ch.kagu.tus.ac.jp (T. Yoshimura). 0021-9797/$ – see front matter 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2004.03.002
Abstract The interactions of cationic gemini surfactants, 1,2-bis(alkyldimethylammonio)ethane dibromide (m-2-m: m is hydrocarbon chain length, m = 10 and 12), and an anionic polymer, sodium poly(styrene sulfonate) (PSS), have been characterized by several techniques such as tensiometry, fluorescence spectroscopy, and dynamic light scattering. The surface tension of gemini surfactant/PSS mixed systems decreases with surfactant concentration, reaching break points, which are taken as critical aggregation concentrations (cac). The surface tension at the cac of mixtures is higher than that of single surfactants, and it is found that at concentrations above the cac, the surfactant molecules are associated with the polymer in the bulk. The 12-2-12/PSS mixed system shows higher surface activity than both 10-2-10/PSS and the monomeric surfactant of dodecyltrimethylammonium bromide/PSS systems. Fluorescence measurements of these mixed systems suggest the formation of a complex with a highly hydrophobic environment in the bulk of the solution. Additionally, dynamic light scattering measurements show that the hydrodynamic diameter of the 12-2-12/PSS mixed system is smaller than that of PSS only at low concentration, indicating interactions between surfactant and polymer. These result from the electrostatic attraction between ammonium and sulfate headgroups as well as the hydrophobic interaction between their hydrocarbon chains. 2004 Elsevier Inc. All rights reserved.
tant/uncharged polymer mixed systems have been reported, there have been few reports about those of gemini surfactant/polymer mixed systems [14,15]. Gemini surfactants, which have two hydrocarbon chains and two hydrophilic groups in a molecule, reportedly possess unique properties, such as better solubilization, lower Krafft temperatures, lower critical micelle concentration (cmc), greater efficiency in lowering the surface tension, and foaming properties than the conventional monomeric surfactants [16–19]. The purpose of this study is to investigate whether any interaction occurs between cationic gemini surfactant and anionic polymer at air/water interface and in solution. Gemini surfactant is used to investigate the effect of chain numbers of these compounds on interactions with anionic polymer. In this work, we investigate the interactions of cationic gemini surfactant, 1,2-bis(alkyldimethylammonio)ethane dibromide (m-2-m, where m is the hydrocarbon chain length, m = 10 and 12), and an anionic polymer, sodium poly(styrene sulfonate) (PSS), by measuring surface tension, fluorescence spectroscopy of pyrene, and dynamic light scattering. In
Journal of Colloid and Interface Science 275 (2004) 618–622 /locate/jcis
Interactions of quaternary ammonium salt-type gemini surfactants with sodium poly(styrene sulfonate)
Keywords: Cationic gemini surfactant; Anionic polyelectrolyte; Interaction; Aggregate; Surface tension; Fluorescence; Hydrodynamic diameter
1. Introduction The study of interactions between surfactants and polymers is an active field of interest in colloid science [1]. The mixtures of surfactants and polymers are used in the fields such as paints and drilling muds, etc. Important information on surfactant and polymer interathe bulk is currently being provided by techniques such as surface tension, neutron and X-ray reflection, ellipsometry, and surface rheology [2]. The mixtures of oppositely charged surfactants and polymers are very sensitive indicators of interaction [3–5]. The interaction between the cationic surfactant alkyltrimethylammonium bromide or chloride and anionic polymer such as polyacrylamide sulfonate, polystyrene sulfonate (PSS), DNA and xanthan has been investigated [6–13]. Although many studies of the properties of the conventional monomeric surfac* Corresponding author. Fax: +81-3-32352214.