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

Abstract

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.

Experimental evidence for an optical interference model for vibrational sum frequency generation on multilayer organic thin film systems. I. Electric dipole approximation

“…[26][27][28][29] X-ray spectroscopic techniques have also been demonstrated as surface sensitive probes. For example, near edge x-ray absorption fine structure (NEXAFS) [30][31][32] or X-ray photoelectron emission microscopy (X-PEEM) 33 can be used to deduce structure at an interface. However, they are also limited to sampling only the exposed interfaces.…”

Highly resolved transmission infrared microscopy in polymer science

“…Both quantitative chemical information, and morphological or structural information, such as orientation [25][26][27], is available, and spatial resolution better than 40 nm can now be achieved [28], with significantly lower level of beam damage than that observed in EELS.…”

Temperature effect on a rubbed polyimide alignment layer

“…7 A variation on this idea suggests that the rubbing pressure need not be so high as to induce order deep into the polyimide layer, but rather only near the surface. 8,9 The depth of this oriented alignment region is an important issue. [9][10][11][12] Some insist that alignment in this surface region is complete, and stronger rubbing just increases the depth of the aligned region.…”