Gemini surfactants have enhanced interfacial properties with respect to their single chain counter parts. Thus, their behavior in water is of great relevance for industrial applications and for nanodevice pro- duction. In this work we studied the shape evolution of alpha,omega-bis(N-dodecyl-N,N-dimethyl ammonium bromide) (i.e. 12-s-12) micelles as a function of spacer length (s = 3, 6, 12) and concentration. Small angle X-rays scattering (SAXS) and electron spin resonance (ESR) spectroscopy were the methods used to obtain complementary information. SAXS curves were analyzed with the GENFIT software over two orders of magnitude in concentration. The fitting evidenced a shape evolution from globular objects, to worm like aggregates and finally to lamellae. The fluidity and polarity of molecular environment were investigated by appropriately tailored spin probes. The ESR spectral parameters changed in correspondence to the shape transition highlighted by SAXS. In addition, data on local polarity and motional freedom suggested that the longer spacers tend to fold toward the internal region of micelles.
Physico-chemical properties of gemini micelles studied by X-ray scattering and ESR spectroscopy / Falsini, S.; Ciani, L.; Arcangeli, A.; Cola, E. Di; Spinozzi, Francesco; Ristori, S.. - In: COLLOIDS AND SURFACES. A, PHYSICOCHEMICAL AND ENGINEERING ASPECTS. - ISSN 0927-7757. - STAMPA. - 472:(2015), pp. 101-108. [10.1016/j.colsurfa.2015.02.034]
Physico-chemical properties of gemini micelles studied by X-ray scattering and ESR spectroscopy
SPINOZZI, Francesco;
2015-01-01
Abstract
Gemini surfactants have enhanced interfacial properties with respect to their single chain counter parts. Thus, their behavior in water is of great relevance for industrial applications and for nanodevice pro- duction. In this work we studied the shape evolution of alpha,omega-bis(N-dodecyl-N,N-dimethyl ammonium bromide) (i.e. 12-s-12) micelles as a function of spacer length (s = 3, 6, 12) and concentration. Small angle X-rays scattering (SAXS) and electron spin resonance (ESR) spectroscopy were the methods used to obtain complementary information. SAXS curves were analyzed with the GENFIT software over two orders of magnitude in concentration. The fitting evidenced a shape evolution from globular objects, to worm like aggregates and finally to lamellae. The fluidity and polarity of molecular environment were investigated by appropriately tailored spin probes. The ESR spectral parameters changed in correspondence to the shape transition highlighted by SAXS. In addition, data on local polarity and motional freedom suggested that the longer spacers tend to fold toward the internal region of micelles.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
