POLARIZED XANES STUDIES ON THE RUBBED POLYIMIDE FOR LIQUID-CRYSTAL ALIGNMENT - NEW APPLICABILITY TO THE TRIBOLOGY OF THE POLYMER SYSTEMS

The surface structure of rubbed polyimides, which is responsible for the homogeneous alignment of liquid crystal molecules, was examined with use of polarized XANES spectroscopy. Our first experiment was conducted on the odd-even effect of BPDA-Cn (biphenyl-3,3',4,4'-tetracarboxylic dianhydride/n-alkyl diamine) type polyimide; BPDA-Cn type polyimide with even number alkylene chain induces a large LC pretilt angle and the one with odd number alkylene chain does almost 0 degree LC pretilt angle. XANES spectra have successfully revealed the surface-structure difference between odd- and even-number BPDA polyimides, one is trans-cisoid type and the other is trans-transoid type, respectively.