AVS 45th International Symposium
    Applied Surface Science Division Wednesday Sessions
       Session AS-WeA

Invited Paper AS-WeA3
Correlations of the Structure and Mechanical Properties of Polymer Surfaces: Combined Sum Frequency Generation-Surface Vibrational Spectroscopy and Atomic Force Microscopy Studies

Wednesday, November 4, 1998, 2:40 pm, Room 307

Session: Polymer Surfaces, Films and Interfaces
Presenter: G.A. Somorjai, University of California, Berkeley
Authors: G.A. Somorjai, University of California, Berkeley
D. Gracias, University of California, Berkeley
D. Zhang, University of California, Berkeley
Correspondent: Click to Email
Vibrational spectroscopy by sum frequency generation (SFG) is a non-linear optical technique that is totally monolayer sensitive and can be employed for studies of solid-liquid, solid-solid, and solid-gas interfaces. It provides information about the surface structure and orientation of molecules at the interface. Atomic force microscopy permits measurements of the elastic moduli and the friction coefficient of interfaces with excellent spatial resolution. We utilized both techniques to investigate polyethylene (low and high density), polypropylene (atactic, isotactic) surfaces, and a polymer blend, Biospan-S, in air and in liquids and as a function of temperature. The structure and orientation of CH@sub 2@ and CH@sub 3@ groups at the interface readily identify polyethylene and polypropylene types. Structural changes that occur near and at the glass transition temperatures are detectable. The friction coefficients and elastic moduli correlate well with changes of surface structure. Biospan-S undergoes structural changes when placed in an aqueous solution from air resulting in the migration of the hydrophilic polymer components to the surface. Good correlations of these changes with variations of contact angle were found. AFM detects phase segregation as the composition of the polymer blend is altered.