(223b) Interfacial Phenomena of Complex Fluids and Functional Thin-Films Under Confinement

The Surface Force Apparatus (SFA) is a highly versatile method for directly measuring the interaction forces between two surfaces/interfaces with sub-nanometer resolution in distance and 10 picoNewtons in force. Both the normal and shear force between the surfaces can be measured as well as the refractive index of the films to ±0.005. Coupled with neutron and X-ray spectoroscopy, the structure, function, and properties of interfacial films can be characterized with near molecular resolution. This talk will highlight a few systems (described below) as a means to elucidate the quantitative capabilities of high resolution force spectroscopy coupled with small angle scattering to determine the properties and dynamics of a variety of complex interfacial films under nano-confinement.

Specific systems will include:

1. ultra-high density polymer brushes grown by ATRP for improved lubrication and wear (although polymer film relaxation times exceed hours, ultra low friction is observed)

2. weakly adsorbed "bottle brush" type polyelectrolytes for improved cement flow properties (in this case force spectroscopy proves extremely informative for understanding the adsorbed layer properties or even if there is an adsorbed polymer layer under pore solution conditions of high alkalinity and ionic strength)

3. the complexities of the DPPC - cholesterol phase diagram and dramatic changes in headgroup hydration between the gel and Lo phase (under what conditions does a PC lipid appear a PE lipid?)