Flexibility of aromatic polyimides and polyamidoacids

Syntheses and characteristics of polyimides for the applications to alignment film for liquid crystal display

“…Figures 1 and 2 illustrate typical SHG signals of rubbed PMDA–BAPP, whose chains adopt zigzag and planar conformations, and those of PMDA–BAB, whose chains adopt helical and nonplanar conformations, respectively. The surface orientation of polyimides, PMDA–BAB and PMDA–BABP, whose chains adopt zigzag and planar conformations, were less improved by rubbing treatment than that of polyimides, PMDA–BAPP, PMDA–BAPS, and PMDA–BAPHF, whose chains adopt helical and nonplanar conformations, because the polyimide chains of zigzag and planar conformation are easily packed 20–22. In Figure 3, the polar functionality has been measured by atomic force microscopy on the polymer alignment layer surfaces before and after rubbing treatment for both PMDA–BABP and PMDA–BAB.…”

Preparation of High Performance Copolyimide Fibers via Increasing Draw Ratios

“…The diamines, p‐ PDA, ODA, and BIA, are the nucleophilic regents, and their reactivities with BPDA increase with increasing ionization potential and larger charge density of the amino nitrogen, which can be assumed by increasing pK a values . The pK a values of PDA and ODA are 6.08 and 5.20, respectively, indicating that the reactivity of PDA is higher than that of ODA. Additionally, the charge density in amino nitrogen of ODA increases due to the joint oxygen atom charge donor, while the charge density in amino nitrogen of BIA decreases because the charge transfers from amino nitrogen to conjugate system in BIA, resulting in higher reactivity of ODA …”

High performance polyimides for applications in microelectronics and flat panel displays

“…115 Second, in the PAAs all the backbone skeletal valence angles, such as ∠ C ar -C-N, ∠C-N-C ar , ∠C ar -O-C ar , and ∠C ar -C-C ar are equally to be 120 ο . 116 Finally, the precursors are alternatively linked by their possible isomeric repeat units. For PMDA-ODA PAA, the chemical repeat units have two diff-erent isomeric structures: meta and para isomeric units.…”

“…[65][66][67][68][69][70][71][72][73]95,124,125,155,156,[160][161][162][163][164][165][166][167] Such PI film surfaces need to be treated if they are to produce a uniform alignment of LC molecules with a defined range of pretilt angle values. [37][38][39][40][41][42]55,83,84,[108][109][110][111][112][113][114][115][116][117][118][119][120][121][122] At present, a rubbing process using a velvet fabric is the only technique adopted in the LC display industry to treat PI film surfaces for the mass-production of flat-panel LC display devices. This process has become the method of choice because of its simplicity and the controllability with this method of both the LC anchoring energy and the pretilt...…”