Effect of ionization on the behavior of n-eicosanephosphonic acid monolayers at the air/water interface. Experimental determinations and molecular dynamics simulations.

Monolayers of n-eicosanephosphonic acid, EPA, were studied using a Langmuir balance and a Brewster angle microscope at different subphase pH values to change the charge of the polar headgroups (Zav) from 0 to -2. Molecular dynamics simulations (MDS) results for |Zav| = 0, 1, and 2 were compared with the experimental ones. EPA monolayers behave as mixtures of mutually miscible species (C20H41-PO3H2, C20H41-PO3H(-), and C20H41-PO3(2-), depending on the subphase pH). The order and compactness of the monolayers decrease when increasing |Zav|, while go from strongly interconnected by phosphonic-phosphonic hydrogen bonds (|Zav| = 0-0.03) through an equilibrium between the total cohesive energy and the electrostatic repulsion between the charged polar groups (0.03 < |Zav| < 1.6) to an entirely ionic monolayer (|Zav| ≈ 2). MDS reveal for |Zav| = 0 that the chains form spiralled nearly rounded structures induced by the hydrogen-bonded network. When |Zav| ≈ 1 fingering domains were identified. When Z ≈ 2, the headgroups are more disordered and distanced, not only in the xy plane but also in the z direction, forming a rough layer and responding to compression with a large plateau in the isotherm. The monolayers collapse behavior is consistent with the structures and domains founds in the different ionization states and their consequent in-plane rigidity: there is a transition from a solid-like response at low pH subphases to a fluid-like response at high pH subphases. The film area in the close-packed state increases relatively slow when the polar headgroups are able to form hydrogen bonds but increases to near twice that this value when |Zav| ≈ 2. Other nanoscopic properties of monolayers were also determined by MDS. The computational results confirm the experimental findings and offer a nanoscopic perspective on the structure and interactions in the phosphonate monolayers.

[1]  W. Verboom,et al.  Heterogeneous Acid Catalysis Using a Perfluorosulfonic Acid Monolayer-Functionalized Microreactor , 2013, Journal of Flow Chemistry.

[2]  Marco Bernardi,et al.  Extraordinary sunlight absorption and one nanometer thick photovoltaics using two-dimensional monolayer materials. , 2013, Nano letters.

[3]  E. Schulz,et al.  Intermediate structures for higher level arrangements: catching disk-like micelles in decane phosphonic acid aqueous solutions. , 2013, The journal of physical chemistry. B.

[4]  K. Landfester,et al.  From soft to hard: the generation of functional and complex colloidal monolayers for nanolithography , 2012 .

[5]  Stephen Mann,et al.  Designs for life: protocell models in the laboratory. , 2012, Chemical Society reviews.

[6]  N. Hassan,et al.  Hydrogenated/fluorinated catanionic surfactants as potential templates for nanostructure design. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[7]  C. Hall,et al.  Simulation of micelle formation in the presence of solutes. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[8]  P. Schulz,et al.  The effect of the hydrocarbon–water interface structure on the behavior of an emulsion stabilized with dodecanephosphonic acid , 2010 .

[9]  P. Schulz,et al.  Inversion Properties of n-Alkane Phosphonic Acids Stabilized Emulsions: HLB Dependence , 2009 .

[10]  Reinhard Miller,et al.  Langmuir monolayers of a hydrogenated/fluorinated catanionic surfactant: from the macroscopic to the nanoscopic size scale. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[11]  Y. Marcus.  Effect of ions on the structure of water: structure making and breaking. , 2009, Chemical reviews.

[12]  G. Prieto,et al.  Surface films of short fluorocarbon-hydrocarbon diblocks studied by molecular dynamics simulations: Spontaneous formation of elongated hemimicelles. , 2009, Journal of colloid and interface science.

[13]  T. Witten,et al.  Lateral stress relaxation and collapse in lipid monolayers. , 2008, Soft matter.

[14]  S. Kundu,et al.  Fatty acid monolayer dissociation and collapse: Effect of pH and cations , 2008 .

[15]  F. Müller-Plathe,et al.  Molecular dynamics simulations of heptyl phosphonic acid: a potential polymer component for fuel cell polymer membrane. , 2008, The journal of physical chemistry. B.

[16]  R. Larson,et al.  Comparing experimental and simulated pressure-area isotherms for DPPC. , 2008, Biophysical journal.

[17]  Teiji Kato,et al.  Temperature and compression rate independent domain shape in Langmuir monolayers of di-n-dodecyl hydrogen phosphate at the air-water interface. , 2008, Journal of colloid and interface science.

[18]  R. Raphael,et al.  Solution pH alters mechanical and electrical properties of phosphatidylcholine membranes: relation between interfacial electrostatics, intramembrane potential, and bending elasticity. , 2007, Biophysical journal.

[19]  J. Ralston,et al.  The formation and stability of self-assembled monolayers of octadecylphosphonic acid on titania , 2006 .

[20]  Shiling Yuan,et al.  Molecular dynamics studies on monolayer of cetyltrimethylammonium bromide surfactant formed at the air/water interface , 2006 .

[21]  A. Hoffmann,et al.  Phosphonic acid monolayers for binding of bioactive molecules to titanium surfaces. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[22]  D. E. Bryant,et al.  On the origin of the Murchison meteorite phosphonates. Implications for pre-biotic chemistry. , 2006, Chemical communications.

[23]  Chris Oostenbrink,et al.  A biomolecular force field based on the free enthalpy of hydration and solvation: The GROMOS force‐field parameter sets 53A5 and 53A6 , 2004, J. Comput. Chem..

[24]  R. Côté,et al.  Quantum reflection engineering: The bichromatic evanescent-wave mirror , 2003 .

[25]  Chaoyang Jiang,et al.  Monolayer formation of alkyl chain-containing phosphoric acid amphiphiles at the air/water (pH 5.6) interface: influence of temperature and cations. , 2002, Journal of colloid and interface science.

[26]  Berk Hess,et al.  GROMACS 3.0: a package for molecular simulation and trajectory analysis , 2001 .

[27]  K. Luthman,et al.  Effect of molecular charge on intestinal epithelial drug transport: pH-dependent transport of cationic drugs. , 1999, The Journal of pharmacology and experimental therapeutics.

[28]  R. Dluhy,et al.  Reflection–absorption FT-IR spectroscopy of pentadecanoic acid at the air/water interface , 1999 .

[29]  D. K. Schwartz,et al.  SUBMONOLAYER ISLAND NUCLEATION AND GROWTH KINETICS DURING SELF-ASSEMBLED MONOLAYER FORMATION , 1998 .

[30]  J. Zasadzinski,et al.  Protein and lipid interactions in lung surfactant monolayers , 1997 .

[31]  Berk Hess,et al.  LINCS: A linear constraint solver for molecular simulations , 1997, J. Comput. Chem..

[32]  D. K. Schwartz,et al.  Self-assembled monolayer growth of octadecylphosphonic acid on mica , 1996 .

[33]  J. Penfold,et al.  Neutron and X-ray reflectometry of interfacial systems in colloid and polymer chemistry , 1996 .

[34]  A. Schwartz,et al.  A plausibly prebiotic synthesis of phosphonic acids , 1995, Nature.

[35]  D. van der Spoel,et al.  GROMACS: A message-passing parallel molecular dynamics implementation , 1995 .

[36]  J. Lu,et al.  Detailed Structure of the Hydrocarbon Chain in a Surfactant Monolayer at the Air/Water Interface: Neutron Reflection from Hexadecyltrimethylammonium Bromide , 1995 .

[37]  J R Cronin,et al.  Alkyl phosphonic acids and sulfonic acids in the Murchison meteorite. , 1992, Geochimica et cosmochimica acta.

[38]  P. Kollman,et al.  Settle: An analytical version of the SHAKE and RATTLE algorithm for rigid water models , 1992 .

[39]  P. Schulz.  Steric fitting of the rodlike micelle size , 1992 .

[40]  R. Thomas,et al.  Structure of a tetradecyltrimethylammonium bromide layer at the air/water interface determined by neutron reflection , 1992 .

[41]  Dirk Hoenig,et al.  Direct visualization of monolayers at the air-water interface by Brewster angle microscopy , 1991 .

[42]  F. F. Aplan,et al.  The influence of point defects on the floatability of cassiterite, III. The role of collector type , 1987 .

[43]  J. Mikroyannidis.  HYDROXY AND/OR CARBOXY SUBSTITUTED PHOSPHONIC AND BISPHOSPHONIC ACIDS USABLE AS CORROSION AND SCALE INHIBITORS , 1987 .

[44]  M. Tomoaia-Cotisel,et al.  Insoluble mixed monolayers: III. The ionization characteristics of some fatty acids at the air/water interface , 1987 .

[45]  A. Petrov,et al.  Self-Assembly and Phase Behavior of Short Chain Phosphonic Acid-Water Systems in a Wide Concentration Range Microscopic, NMR, and X-ray Diffraction Studies , 1982 .

[46]  P. Baglioni,et al.  On the mechanism of collapse of monolayers of macromolecular substances: poly(l, d, and dl)alanine , 1981 .

[47]  H. Ries.  Stable ridges in a collapsing monolayer , 1979, Nature.

[48]  N. Gershfeld,et al.  The surface chemistry of monooctadecyl phosphate at the air/water interface. A study of molecular aggregation in monolayers. , 1967, Journal of colloid and interface science.

[49]  H. C. Parreira.  The surface chemistry of alkyl phosphoric acids , 1965 .

[50]  G. M. Kosolapoff.  Isomerization of Alkylphosphites. III. The Synthesis of n-Alkylphosphonic Acids , 1945 .

[51]  Teiji Kato,et al.  Temperature dependent dendritic domain shapes in Langmuir monolayers of tetradecanoyl N-ethanolamide at the air-water interface. , 2011, Journal of colloid and interface science.

[52]  R. Thomas,et al.  Surfactant layers at the air/water interface: structure and composition. , 2000, Advances in colloid and interface science.

[53]  J. Lu,et al.  Structure of hydrocarbon chains in surfactant monolayers at the air/water interface: neutron reflection from dodecyl trimethylammonium bromide , 1996 .

[54]  H. Berendsen,et al.  Interaction Models for Water in Relation to Protein Hydration , 1981 .