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Abstract
A novel diamine with a side-chain containing naphthalimide ring and non-polar alkyl end group, N-octyl-4-(3,5-dinitrobenzoyl)-amido-1,8-naphthalimide (N8), was synthesised and its chemical structure was confirmed by FTIR (fourier transform infrared) spectroscopy and nuclear magnetic resonance spectroscopy (1H-NMR). Then, a new family of polyimides (PIs) containing naphthalimide unit in the side-chains has been successfully synthesised by reaction of 4,4′-oxydiphthalic anhydride (ODPA) and 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) with the novel functional diamine N8. The obtained polymers showed excellent solubility in a broad range of solvents, including tetrahydrofuran. Thermal properties of polymers were good enough to permit the use of these PIs on liquid-crystal displays (LCDs) applications. Alignment films obtained by casting offered outstanding rubbing-resistant ability, meanwhile kept the pretilt angle high above 89°. The PI seems to be prospective materials for alignment layers in LCDs.
Acknowledgements
This work was supported by 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).