Fast charged carrier mobility of a triphenylene-based polymer film possessing nematic order

A polymer film was prepared by the photopolymerization in a discotic nematic (ND) mesophase of a mixture of the polymerizable triphenylene mesogen isomers. It was found that the film shows a relatively fast mobility of charged carrier (10-3 cm2V-1s-1), which is probably faster than that of the monomeric ND mesophase. The microscopic domains in the film were found to keep the liquid crystalline order even after the polymerization evidenced by the IR spectra showing the small decrease in the local order parameter and by the X-ray diffraction (XRD) patterns comparable to those before the polymerization. It was indicated that in the photopolymerization, the long range order of molecules can be almost remained, the short range one is variant and, thus, such an in-situ liquid crystalline polymerization could lead to the enhancement of charge transport efficiency. Furthermore, the polymerized film was applied to a simple electroluminescent device to reveal that it certainly works as a hole transport layer because the luminescence is clearly induced under bias.