Nonionic Fluorinated Surfactant Removal from Mesoporous Film Using sc-CO2

Synchrotron Scattering Methods for Nanomaterials and Soft Matter Research

This article aims to provide an overview of broad range of applications of synchrotron scattering methods in the investigation of nanoscale materials. These scattering techniques allow the elucidation of the structure and dynamics of nanomaterials from sub-nm to micron size scales and down to sub-millisecond time ranges both in bulk and at interfaces. A major advantage of scattering methods is that they provide the ensemble averaged information under in situ and operando conditions. As a result, they are complementary to various imaging techniques which reveal more local information. Scattering methods are particularly suitable for probing buried structures that are difficult to image. Although, many qualitative features can be directly extracted from scattering data, derivation of detailed structural and dynamical information requires quantitative modeling. The fourth-generation synchrotron sources open new possibilities for investigating these complex systems by exploiting the enhanced brightness and coherence properties of X-rays.

Spontaneous self-assembly and structure of perfluoroalkylalkane surfactant hemimicelles by molecular dynamics simulations

Fully atomistic molecular-dynamics (MD) simulations of perfluoroalkylalkane molecules at the surface of water show the spontaneous formation of aggregates whose size and topography closely resemble the experimentally observed hemimicelles for this system. Furthermore, the grazing incidence X-ray diffraction (GIXD) pattern calculated from the simulation trajectories reproduces the experimental GIXD spectra previously obtained, fully validating the MD simulation results. The detailed analysis of the internal structure of the aggregates obtained by the MD simulations supports a definite rational explanation for the spontaneous formation, stability, size, and shape of perfluoroalkylalkane hemimicelles at the surface of water.

Evidence of lying molecules in the structure of the most condensed phase of semi-fluorinated alkane monolayers

Semifluorinated alkanes are known to form peculiar nano-structured monolayers on the surface of water. A comprehensive analysis of in situ Grazing Incidence Small Angle X-ray Scattering (GISAXS) proves that the structure of their condensed phase consists of domains of upright molecules surrounded by lying down molecules. Such a model explains the non-coalescence of the domains and is in agreement with the high resolution AFM images of monolayers at the surfaces of solid substrates. The interaction of the lying molecule dipoles with the dipole of the water surface is proposed to explain the observed structuration.