Hyperbranched polyimide application in liquid crystal alignment layers

Several hyperbranched polyimides (HBPIs) were applied in liquid crystal (LC) alignment layers and exhibited outstanding performance for LC alignment. The maximum pretilt angle was above 8°, and the minimum pretilt angle was 4.2°. The results of atomic force microscope measurement disclosed that a lot of grooves were aligned parallel to the rubbing direction and found that the grooves were not main factor for LC alignment. The LC alignment and pretilt angles are unambiguously associated with the intrinsic HBPI chemical structures. The results of thermal gravimetric analysis and ultraviolet–visible spectra showed that the HBPIs had good thermal stability and excellent transmittance. T₅ and T₁₀ were higher than 360°C and 400°C, respectively. Copyright © 2012 John Wiley & Sons, Ltd.