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Large pretilt angle induced by an anhydride-terminal hyperbranched polyimide liquid crystal alignment layer

Through the polycondensation of a four-functional amine with pyromellitic dianhydride, a hyperbranched polyimide (HPI) was synthesised in this study. The HPI was used for liquid crystal alignment layers. Wide angle X-ray diffraction measurement showed that the HPI film was amorphous. The morphology of the surface layer of film was determined by atomic force microscopy. It is novel that a larger pretilt angle, above 8°, has been achieved with the rubbed HPI alignment layers. This result was different from that in a previous report, in which only a 2.8° pretilt angle was induced by a HPI alignment film.