Ordered (-aadcbbcd-) polyamides were prepared by the direct polycondensation of a pair of symmetric monomers (XabX), bis(2,4,6-trichlorophenyl) isophthalate or bis(2,4,6-trichlorophenyl) adipate (XaaX) and 5-nitroisophthalic acid (XbbX), with a nonsymmetric monomer (YcdY), 4-aminobenzohydrazide, using the activating agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate. The polycondensation was carried out by mixing the monomers all at once, yielding the ordered polyamide with inherent viscosities up to 0.30 dL/g. The authentic ordered and random polyamides were prepared to verify the structures of ordered polyamide. The microstructures of polyamides obtained were investigated by means of 13C NMR spectroscopy, and it has been found that the polyamides obtained had the expected ordered structures.Furthermore, the model reactions were studied in detail to demonstrate the feasibility of ordered polyamidation.

The photo reactivity and photo alignment sensitivity of a fluorine-containing aromatic polyimide, 4,4-(hexafluoroisopropylidene) diphthalic anhydride 2,3,5,6-tetramethyl-1,4-pheny lene diamine (6FDA-TeMPD), were systematically investigated. This polyimide has high heat resistance, high solubility in polar solvents, high optical transparency, and low refractive index. Different molecular ordering structures of 6FDA-TeMPD polyimide were obtained by controlling the type of casting solvent as well as the dry conditions. The photo reactivity of the polyimide obtained under highly volatile preparation conditions is higher than that obtained under lowly volatile conditions. The photo reactivity showed higher dependency on the type of casting solvent than on the heat treatment temperature. The fluorescence spectra show that the polymer condensation increased under 254 nm linearly polarized ultraviolet irradiation. On the other hand, the photo alignment sensitivity did not depend on the polymer cohesiveness, but rather on the residual solvent trace in the polyimide film. Moreover, the photo alignment sensitivity can be increased by reducing the amount of residual solvent in the polymer film.

We review the important features of LC orientation for the alignment layer, namely, production method, alignment mechanisms, and required properties. Photoalignment, which could eliminate the disadvantages of the rubbing method is explored. Applicable materials and techniques for photoalignment are also examined. Many materials for photoalignment layers have been proposed, but polyimide‐based materials are commonly used because of their transparency and insulation properties, which are needed for optical electronic devices. Furthermore, photoisomerization, photodimerization, and photodecomposition as photoalignment methods are reviewed, and specific photoreactive groups and alignment mechanisms are used to induce LC alignment. In summary, polyimides cause photodecomposition and have the following disadvantages; (1) requirement of relatively short‐wavelength ultraviolet (UV) irradiation, (2) difficulty in reorienting polymer chains owing to their rigid polymer matrix, and (3) low‐photo reactivities. The solutions for each disadvantage are already proposed, but the required properties should be determined during material design. Polyimide‐based materials introduced with the azobenzene and cinnamate groups are proposed and found to have the ability of fulfilling the required properties. The mechanism of polyimide photodecomposition is not fully understood. It likely has the advantage in terms of LC alignment stability because of the absence of E/Z isomerization. Therefore, the alignment mechanism and availabilities should be further explored.

The photo-alignment properties of 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based polyimides with sterically hindered diamine component were systematically evaluated, such as 6FDA-3,3'-dimethylbenidine, 6FDA-2,7-diaminofluorene, 6FDA-2,3,5,6-tetramethyl-1,4-phenylene diamine, 6FDA-2,5-diamino-1,4-phenylenediamine, 6FDA-1,4-phenylenediamine, and 6FDA-1,3-phenylenediamine. To evaluate sterically hindered diamine components, the diamine components with varying number of benzyl ring and methyl group were used. The polyimides containing the diamine components with methyl group were well planarity and forming charge transfer complex efficiently. The polyimides showing photo reaction property by linearly polarized ultra violet light induced photo alignment properties, however, the linear structured polyimide induced photo alignment property even it showed poor photo reaction property.