Synthesis of new aromatic polyimides with various side chains containing a biphenyl mesogen unit and their abilities to control liquid-crystal alignments on the rubbed surface

Semi-Alicyclic Polyimides: Insights into Optical Properties and Morphology Patterning Approaches for Advanced Technologies

“…The rubbing process was performed with a device, consisting in a cylinder on which was attached the velvet and the same experimental conditions were kept (100 rot/min). The surface ordering induced by rubbing is maintained over large areas (> 20x20 µm 2 ), but for a detailed analysis of the textile fiber effect on PI surface topography, the dimensions of the created features were examined on smaller scan areas (Figures 11 and 12). For both PI4 and PI5 there were obtained two dimensional and three-dimensional topographic images before and after surface ordering by rubbing.…”

“…Polyimides (PIs) represent a very important class of high performance synthetic polymers, characterized by stability at elevated temperatures, low thermal expansion, chemical resistance, low dielectric constant, high breakdown voltage, good optical transparency, high adhesion and dimensional stability [1][2][3]. Therefore, they have found widespread applicability: in microelectronics -as interlayer dielectrics, in aircraft industry -as thermoresistant components and in optoelectronics -as optical waveguides.…”

“…An intensive research effort has been undertaken to counteract these shortcomings by designing their structure, including: (1) increasing flexibility along the polymer chain by employment of flexible (e.g. -O-,-SO2-, -CH2-, NHCO-) or less symmetric links, such as meta-or ortho-catenated aromatic units, (2) introducing bulky pendant groups and biphenyl units onto the backbone, and (3) utilizing fluorinated monomers [12]. One of the most successful approaches to enhance transparency, to decrease the dielectric constant and simultaneously to improve solubility consisted in incorporation of aliphatic monomers in the PI backbone, which lead to development of a new type of PIs, namely aliphatic ones [13][14][15][16][17], but in this case the thermal stability is compromised [14].…”

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

“…14,18 The LC alignment properties such as the pretilt angle and electro-optical (E-O) performance on polyimide surfaces are known to be affected by the molecular structure of the polyimide such as the flexibility of the polymer backbone, isomeric structure of the mesogen end groups, spacer length, and spacer conformation in the side chains. 22 For example, the pretilt angle of the LCs on polyimide surfaces with rigid aromatic side groups is 0.6 o , while that of the LCs on polyimide surfaces with flexible alkyl side groups is high above 89.6 o . 23 The different E-O properties of the LC cells made from polyimides having flexible n-alkyl side groups and fluorinated side groups were also reported.…”

Soluble Polyimide Containing a Photoreactive 2‐Styrylpyridine Derivative as the Side Group: Synthesis and Characterization

“…[1][2][3][4][5] This mechanical process, however, suffers from shortcomings such as the generation of dust, electrostatic problems, and a poor control over the rubbing strength. [6][7][8][9] Some photo-induced LC alignment concepts have been reported in connection with these disadvantages. [10][11][12][13][14] Studies of the photoalignment have been based on photocyclodimerizations, transcis photoisomerizations, and photodegradations by using linearly polarized UV light (LPUVL).…”