Polymer Surface Characterization Using Ultrasoft X-ray Absorption Spectroscopy Andy Marsh April 5, 2000 Physical Chemistry Seminar

Outline Motivation for Research Ultrasoft X-ray Absorption Spectroscopy Polymer Surface Characterization Using USXAS Summary and Future Research

Why Study Polymer Surfaces? Polymers are used commercially in many interfacial applications, which range from coatings to microelectronic devices Polymer surface properties have an impact on the behavior of the interfaces Characterization of the interactions of polymers at these interfaces will aid in materials design

Polymer Surface Characterization Techniques X-ray Photoelectron Spectroscopy –chemical composition and bonding Secondary Ion Mass Spectrometry –chemical composition Electron Energy Loss Spectroscopy –chemical bonding Atomic Force Microscopy –surface topography

Ultrasoft X-ray Absorption Spectroscopy Element-specific technique which is sensitive to the types of bonds present in the polymer Angular dependence of resonance intensities allows for the determination of substituent and backbone orientation Ability to probe both the surface (electron yield) and bulk (fluorescence yield) of the material

X-ray Absorption

Synchrotron Radiation Electrons move in a closed path with the aid of magnets and when accelerated give off light at points tangent to the path Light emitted by the electrons consists of wavelengths ranging from infrared to X- rays Light is INTENSE, highly FOCUSED, and linearly POLARIZED

National Synchrotron Light Source

The Electromagnetic Spectrum

Dow/NIST Materials Characterization Endstation

Polystyrene USXAS D.A. Fischer, G.E. Mitchell, A.T. Yeh, J.L. Gland Appl. Surf. Sci. 1998, 133, 58.

Angular Dependence of Spectra

Pendant Phenyl Ring Orientation

Polyvinazene Polymer based on 2-vinyl-4,5 dicyanoimidazole Imidazole H has a pK a of about 5.5 Can be easily processed into films

Polyvinazene C-K-Edge

Polyvinazene N-K-Edge

XPS versus USXAS

Polymer Sample Orientation

Summary USXAS provides an interesting perspective when used to study polymers which contain several different atoms, i.e. both C and N USXAS shows sensitivity to different bonds present in the polymer, i.e. C-C vs. C=C USXAS can be used to determine the orientation of substituents on the polymer backbone

Future Research Directions Further characterize polyvinazene using EELS and AFM and other polymers using the techniques mentioned Characterize interactions of metals and ceramics with polyvinazene and other polymers

Acknowledgements Dr. John Gland The Gland Group, especially Dr. Aaron Gabelnick and Mr. Daniel Burnett Dr. Dan Fischer Dr. Paul Rasmussen and Ms. Jessica Kelley IGERT Materials Program

Polymer Sample Orientation

XPS of Polyvinazene