A preliminary inquiry into the conformation of the side chains on polyimide film and the mechanism of the vertical alignment of liquid crystals induced by polyimides with side chains

Abstract

A series of functional diamines, with various side chain structures and length, were designed and synthesised. Four polyimides (PIs) were copolymerised from pyromelitic dianhydride, p-phenylenediamine and four functional diamines. The conformation of the side chains on the surface of PI film was investigated through X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared dichroic spectroscopy. The results showed that the side chains on the PI film surface aligned outwards in the polymer bulk phase before rubbing. It was found that the length and the contents of the side chains influenced the conformation of the side chains. The interaction between the liquid crystals (LCs) and the side chains on the PI film surface induced the LCs to align vertically.

Keywords:

• polyimide
• alignment layer
• vertical alignment
• liquid crystal

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 50973067, 51173115, 21172161), the Ministry of Education (the Foundation for Ph.D. training, Grant No. 20110181110030) of China and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, and Science (No. 20071108-18-12).