Fourier transform infrared study on black soap films

Abstract

This paper is dedicated to Professor Camille Sandorfy on the occa.siorz of his 65th birthdayJ u~z o UMEMURA, MUTSUO MATSUMOTO, TAKESHI KAWAI, and TOHRU TAKENAKA. Can. J. Chem. 63, 1713Chem. 63, (1985. Fourier transform infrared (FT-IR) spectra in the range 3800-2800 cm-' have been recorded of the first and second black films in air prepared from aqueous solutions of sodium dodecylsulfate (SDS) without and with the addition of sodium chloride, respectively. It is found that in both films the methylene chains of SDS, which are located outside the aqueous core of the sandwich structure, are in an oriented liquid crystalline state. In a first black film, the thickness of the aqueous core is determined to be 9.6 nm, by recording polarized infrared spectra with various angles of incidence to the film surface, and by analyzing them with the aid of thin layer optics. It is found that this value varies in the range 5 -10 nm from film to film.The extinction coefficients of the aqueous core are also examined. In the second black film, the thickness of the aqueous core is found to be about I nm. The OH stretching band of water in the second black film appears at appreciably higher wavenumbers (by 60 cm-') than those of the first black film, indicating a high ionic strength in the aqueous core. In both black films, there is no sign of molecular orientation or rigidified structure of water.J u~z o UMEMURA, MUTSUO MATSUMOTO, TAKESHI KAWAI et TOHRU TAKENAKA. Can. J. Chem. 63, 1713 (1985). On a enregistrt les spectres infrarouges par transformation de Fourier dans la region de 3800 h 2800 cm-I des premier et deuxikme films noirs dans I'air prCparCs a partir de solutions aqueuses de dodtcylsulfate de sodium (DSS) respectivement avec et sans chlorure de sodium. On a trouvC que dans chacun de ces films, les chaines mtthylknes du DSS, qui sont situtes ti I'exttrieur du noyeau aqueux de la structure en sandwiche, sont dans un Ctat cristallin liquide orientC. En enregistrant les spectres infrarouges polarisCs sous divers angles d'incidence par rapport a la surface du film et en les analysant i i l'aide de principes d'optique pour les couches minces, on a CvaluC que I'Cpaisseur du noyeau aqueux du premier film noir est tgale ti 9,6 nm. On a trouvt que cette valeur varie de 5 a I0 nm suivant le film. On a aussi examink les coefficients d'extinction des noyeaux aqueux. Dans le deuxikme film noir, on a trouvC que I'tpaisseur du noyeau aqueux est tgale a I nm. Par rapport au premier film noir, la bande de vibration OH de I'eau du deuxikme film noir se trouve a des nombres d'onde beaucoup plus ClevCs (environ 60 cm-I); ce rtsultat indiquerait la prksence d'une force ionique Clevte dans le noyeau aqueux. Dans les deux films noirs, il n'existe aucun signe d'orientation molCculaire ou de structure rigidifite de I'eau.[Traduit par le journal]

Influence of Surfactant Structure on the Drainage of Nonionic Surfactant Foam Films

“…Fourier transform infrared (FT-IR) spectrometer, System 2000 FT-IR (Perkin Elmer Co.) was used to determine the thickness of the foam films according to previous papers (7,17,19). A measuring cell having two CaF 2 windows and a frame was used for measurements in the cell.…”

Unusual buffer action of free-standing nanoscopically confined water

“…The critical micelle concentration of SDS in salt-free aqueous solution is 8.1 Â 10 À3 mol L À1 at 25°C [21]. The dye NR hydrochloride (NRH + Cl À ) was obtained from Aldrich Chemical Co. and purified by recrystallization from methanol.…”

“…1. The nondestructive and highly sensitive molecular spectroscopy techniques such as UV-vis and FTIR spectroscopy were well-suited for the studies of the macroscopic and vertical BSFs [21][22][23]. For the SDS micellar solutions adjusted with HCl/NaOH solutions and NH 3 ÁH 2 O-NH 4 Cl buffer solution, the layers of confined water in the corresponding BSFs were 2.7-6.2 nm thick, and the nanoscopic water exhibited unusual buffer action resistant not only to acidic/alkaline solutions but also to standard buffer solution.…”

Effect of dye molecules on black film stability and property of aqueous core phase

“…Work directed towards soap films of cationic surfactants is lacking due to their instability [10,11]. Liang and coworkers first introduced anionic dye, methyl orange (MO), to an aqueous solution of cationic surfactant cetyltrimethylammonium bromide (CTAB) to obtain stable black films in air and studied the films using molecular spectroscopy [12], which is one of the most powerful techniques for investigating the structure and properties of freestanding black films in air at the molecular level [3,[5][6][7][8][12][13][14][15][16][17][18][19][20][21]. In the meanwhile, the added counterionic tral axis was used to support a soap film for spectrum measurements.…”