X-PEEM Study on Surface Orientation of Stylized and Rubbed Polyimides.

X-ray photoelectron emission microscopy (X-PEEM) was used to study the surface orientation of stylized and rubbed polyimide thin films. Using soft X-rays produced by a synchrotron light source, this technique combines high spatial resolution imaging with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to yield information on the surface orientation of the films. Stylizing is an ideal model of the rubbing process since the local stress acting on the polyimide to orient the molecules can be calculated. The minimum normal stress necessary to orient the surface of BPDA-PDA films was found to be 45 MPa much lower than the bulk yield stress of 200-300 MPa. Studies of the polyimide films oriented by the conventional rubbing method showed lateral inhomogeneities in the orientation of the polymer at the surface.