Invited Paper BI+AS-WeA1
Sum Frequency Generation (SFG) - Vibrational Spectroscopy and Atomic Force Microscopy (AFM) Studies of Biomaterial Liquid and Gas Interfaces. Surface Structures, Compositions and Bonding
The surface monolayers of polyethylene and polypropylene and its blends, polyurethanes with different hydrophilic and hydrophobic endgroups and their blends and pHEMA have been studied by a combination of SFG and AFM. SFG reveals the different surface structures of polyolefins as a function of molecular weight. Changes of chain orientation occur at the glass transition temperature of polypropylene (-10 ËšC). When polyethylene is stretched, the surface becomes rough as the spherulites align in the stretch direction thereby weakening the polymer normal to the stretching direction. pHEMA with polymer groups that are crosslinked and polymer chains that are not exhibit variations of friction coefficients as measured by AFM. The low friction areas can be associated with polymer chains that are not crosslinked that can also be removed by methanol solution. These studies can also be carried out while the surface is under water. AFM reveals phase separation in blends due to the difference in friction coefficients of the two polymer components.