Polymer Bulletin, Vol.70, No.5, 1553-1574, 2013
An insight on the effect of rubbing textile fiber on morphology of some semi-alicyclic polyimides for liquid crystal orientation
Two semi-alicyclic PIs were prepared from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) and the aromatic diamines: 4,4'-oxydianiline (ODA) or 4-(4-{[4-(4-aminophenoxy)phenyl]sulfonyl}phenoxy)aniline (pBAPS). The obtained films are transparent in visible domain, having a cut-off wavelength of 294 nm for poly(BOCA-ODA) and 264 nm for poly(BOCA- p BAPS), respectively. Atomic force microscopy images indicate a better surface organization after rubbing with cotton velvet (V-C) comparatively with cellulose diacetate (V-CD). Contact angle measurements reveal a slight increase of hydrophobicity after patterning as a result of dipolar forces intensification and geometrical constraints of the macromolecular chains. The alignment properties of both PIs, tested with N-(4-methoxybenzylidene)-4-butylaniline, are more obviously for processing with V-C. Also, the contrast between the dark and bright states is higher for poly(BOCA- p BAPS)/V-C comparatively with poly(BOCA-ODA)/V-CD, since its larger surface malleability generates deeper microgrooves.