Correlation of surface molecular composition to nanoscale elastic behavior and topography of stretched polyurethane films

Correlation of the surface molecular composition with the nanoscale elastic behavior and topography of stretched polyurethane films was examined by surface-specific techniques, such as sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). Identification of the SFG spectra of the soft and hard copolymer segments elucidated changes in the molecular composition due to stretching. The surface molecular composition is correlated to AFM results for the roughness and elastic modulus. It is shown that, in addition to molecular reorientation, stretching promotes exposure of hard segments at the surface, and that this is a continuous time-dependent process at constant elongation.