Hydrogen bonded supra-molecular surfactant systems

ERICA PATRICA SCHULZ; ÁNGEL PIÑEIRO GUILLÉN; MARISA A. FRECHERO; OLGA I. PIERONI; JOSE LUIS RODRIGUEZ; ROSANNA M. MINARDI; PABLO C. SCHULZ; JOSÉ MIÑONES CONDE; JOSÉ MIÑONES TRILLO

La Plata

Workshop; Pan-American Advanced Studies Institute on Frontiers in Particulate Media: From Fundamentals to Applications (PASI 2014ç9; 2014

National Science Fundation - CONICET

The self-assembly of supramolecular surfactant systems may be studied with a multi-scale insight: from the macroscopic results of experiments to the nanoscopic perspective of molecular dynamics simulations. This full scope of techniques, with complementary experimental and theoretical results, allowed us to study systems of alkane phosphonic acids, which are diprotic weak acids with some interesting properties as well as many technological and industrial applications. Their charge can be tuned as 0 (R-PO3H2), -1 (R-PO3H-) or -2 (R-PO3=) by changing the medium pH. Micelles Stern layer is connected by hydrogen bonds from charge near 0 up to an average charge of -1. The possibility to form intermolecular hydrogen bonds among the surfactant molecules strongly affects the formation of supramolecular nano-aggregates generating atypical structures such as disk-like molecules and inter-molecular regular order in monolayers. We have studied the formation of n-decane phosphonic acid disk-like micelles in aqueous solution without the addition of a second ionic surfactant (dx.doi.org/10.1021/jp312713e | J. Phys. Chem. B 2013, 117, 6231−6240). Disk-like micelles are seldomly reported in literature and have been proposed as precursors to the formation of lamellar liquid crystals. Besides, we have fully studied monolayers of n-eicosanephosphonic acid on water subphases with different pH values using a Langmuir balance and Brewster angle microscope and molecular dynamic simulations. We have interest findings, such as the presence of small ?islands? floating on an almost free water surface in monolayers with Z = 0 due to the hydrogen bonded phosphonic groups in spiralled structures. To the best of our knowledge, these phenomenons have never been studied systematically through complementary experimental and computational techniques.