The impact of rubbing fabric type on surface roughness and tribological properties of some semi-alicyclic polyimides evaluated from atomic force measurements

The morphology of some polyimides (PI) prepared from a flexible and alicyclic dianhydride, in combination with aromatic diamines was investigated in detail before and after rubbing with two types of fabric: cotton velvet (CV) and cellulose diacetate velvet (CDV). Atomic force microscopy was employed to evaluate the correlation between rubbing-induced grooves in PI film and size/flexibility of textile fibers. For both samples surface isotropy decreased appreciatively with 91% after patterning since the appearance of ordered nanostructures in the direction of rubbing. The angular spectra reveal the generation of a surface anisotropy after rubbing process and a higher surface regularity and uniformity when using CV. This result is confirmed by decrease of texture direction index with 75% and of surface texture aspect ratio with 89%. These parameters together with the rubbing fiber characteristics are key factors in controlling liquid crystal alignment on patterned PI surfaces.