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Synthesis of novel soluble polyimides containing triphenylamine groups for liquid crystal vertical alignment layers

Abstract

A novel functional diamine containing triphenylamine and biphenyl moieties as well as a long alkyl chain, N,N-bis (4-aminophenyl)-4-(dodecyloxy-biphenyl)-4′-aminophenyl ether (B12), was successfully synthesized. A series of novel polyimides (PIs) with triphenylamine units in the polymer backbone were prepared from B12, 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA), and 4,4′-oxydiphthalic anhydride (ODPA) via a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids (PAAs) followed by chemical cyclodehydration. The chemical structures of the intermediates, diamine, and PIs were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). All PIs were amorphous and readily soluble in many organic solvents, including tetrahydrofuran. PI films attained from a casting method showed high transmittance (above 90 %) in the wavelength range 400–700 nm and induced highly uniform vertical alignment of liquid crystals (LCs). PIs-B12 derived from B12, DMMDA, and ODPA exhibited much higher thermal stabilities than with the corresponding PIs-D12 from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of triphenylamine units into the polymer backbone improves the thermal stability of the PIs without deteriorating their solubility.

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Acknowledgments

This work was supported by the National Natural Science Foundation of China (grant no. 51173115) and the Ministry of Education (the Foundation for Ph.D. training, grant no. 20110181110030) of China.

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Correspondence to Yinghan Wang.

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Gong, S., Liu, M., Xia, S. et al. Synthesis of novel soluble polyimides containing triphenylamine groups for liquid crystal vertical alignment layers. J Polym Res 21, 542 (2014). https://doi.org/10.1007/s10965-014-0542-0

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  • DOI: https://doi.org/10.1007/s10965-014-0542-0

Keywords

  • Thermal properties
  • Soluble polyimide
  • Triphenylamine
  • Vertical alignment
  • Liquid crystal