The effect of junction modes between backbones and side chains of polyimides on the stability of liquid crystal vertical alignment

Abstract

Polyimides (PI-N9 and PI-N12) were synthesized from two kinds of functional diamines, whose junction modes between backbones and side chains were different. Side chains of PI-N9 were linked to the backbones with an ether bond spacer; and side chains of PI-N12 were directly linked to the backbones without any spacer. The PI alignment layer surfaces were investigated by atomic force microscopy, surface free energy measurements, X-ray photo-electron spectroscopy and polarized attenuated total reflection Fourier transformed infrared spectroscopy. It was found that PI-N9 lost the vertical alignment capability after high-strength rubbing, while PI-N12 could still induce liquid crystals (LCs) to align vertically under the same condition. The mechanism of the macroscopic molecular orientation of the PI surface is proposed. During the high-strength rubbing process, the side chain could rotate around the flexible ether bond which existed between the side chain and the main chain of PI-N9 and then fell over. Therefore, PI-N9 could not induce the vertical alignment of LCs anymore. But PI-N12 could keep LCs aligning vertically all the time, which proved that the stability of LC alignment induced by PI-N12 was better.

The role of intramolecular and intermolecular hydrogen bonding effect for adenine-containing polyimide films

“…17 The vibration direction of polarized IR beam can give both the in-plane component and out-plane component, which can provide not only in-plane orientation information but also out-plane orientation information of groups. 31 According to the reported works, 32 the peaks of 1720 and 1780 cm −1 are out-of-phase and in-phase stretching vibrations of the carbonyl in imide, respectively. In b-H-MeO-APIs films, the bands around 1610, 1355, and 1511cm −1 can be assigned to the C=N stretching, C-N-C axial stretching, and benzene ring skeleton vibration, respectively.…”

Correlation between the Electrochemical Durability of Pt/C Catalysts and the Surface Functional Groups of the Support Carbon

“…The component at (∼282 eV) present in both spectra has been attributed to the contribution from C−C (sp 3 ). 46 The remaining components, C2 (∼284.6 eV), C3 (∼286.5 eV), C4 (∼288.7 eV), C5 (∼291 eV), and C6 (∼293.5 eV), are ascribed, respectively, to C�C (sp 2 ), CH/C−C, COOH or COO − , π−π* transition, 47 and a highly oxidized species such as C−F, 48 possibly attributed to the production process, which is unique for C 2 . Small variations between the relative distributions of components are seen, especially in the C3 and C5 components.…”