Effect of the functional diamine structure on the properties of a polyimide liquid crystal alignment film

RSC Advances Pub Date: 2015-03-02 DOI: 10.1039/C4RA16997B

Abstract

A novel functional diamine containing triphenylamine moiety and biphenyl as well as a long alkyl chain, 4-dodecyloxy-biphenyl-4′,4′′-diaminotriphenylamine (DBDTA), was synthesized and characterized. A series of polyimides (PIs) were copolymerized from DBDTA, 3,3′-dimethyl-4,4′-methylenedianiline (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA) via a one-step method. The chemical structures of the diamine and PIs were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). Properties such as the solubility, rubbing resistance, thermal stability and pre-tilt angle of the PIs were investigated. Furthermore, the results were compared with the PIs-BZA derived from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA). The PIs-TPA derived from DBDTA exhibited better transparency and thermal stability than the PIs-BZA from DBPDA. When the content of functional diamines was only 10%, the PI1-TPA derived from DBDTA displayed better solubility than the PI1-BZA from DBPDA. In addition, all PIs could induce uniform vertical alignment of the liquid crystals (LCs) before and after the rubbing process, but PI1-BZA only induced parallel alignment of the LCs after rubbing process. It is suggested that the PI1-TPA film is more resistant to the rubbing process than PI1-BZA.

Graphical abstract: Effect of the functional diamine structure on the properties of a polyimide liquid crystal alignment film
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