Quaternary copolyimides with various monomer contents: Thermal property and optical transparency

Recent Trends on Transparent Colorless Polyimides with Balanced Thermal and Optical Properties: Design and Synthesis

“…High temperature resistant colorless polymers as a plastic substrate are drawing great attention due to their extensive application in image display devices, liquid crystal alignment layers, optical films, organic photovoltaics, flexible printing circuit boards, touch panels, and other optoelectronic devices. [1][2][3][4][5][6][7][8][9][10][11][12][13] In addition, the display devices could be made markedly lighter, more robust, and more flexible if the current fragile inorganic glass substrates (400-700 µm thick) are replaced with plastic substrates (<50 µm thick). The essential requirements for an optically transparent polymer for plastic substrates are to have a high glass transition temperature (T g ) (>300 °C) for thermal processing, excellent optical transparency in the UV-visible wavelength range, good solubility, dimensional stability, film ductility and film-forming process compatibility, solvent resistance, and low coefficient of thermal expansion (CTE).…”

Synthesis and properties of novel colorless and thermostable polyimides containing cross‐linkable bulky tetrafluorostyrol pendant group and organosoluble triphenylmethane backbone structure

“…Common methods include the introduction of alicyclic structures, fluorine atoms, bulky substituents, twisted asymmetric structures and flexible links, and so forth, which could depress the close packing of polymer chains and disrupt the conjugation between the molecular chains to reduce the formation of CTC, and thereby increasing the light transmittance of the film. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] However, the molecular structure designs that are in favor of optical transparency usually impair the thermal performance of the materials to some extent. For example, Zhou et al synthesized a novel monomer trans-1,4-bis (2,3-dicarboxyphenoxy) cyclohexane dianhydride with alicyclic structure, which reacted with a variety of diamines to prepare a series of PIs.…”

Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4‐diaminocyclohexane via aromatic nucleophilic substitution polymerization

“…For the latter, salts can be formed using alicyclic diamines as monomers, such as 1,4-diaminocyclohexane (CHDA), in traditional dianhydride/diamine polycondensation due to the higher basicity of alicyclic diamines compared with aromatic diamines. [22][23][24][25][26][27] Thus, additional treatments are needed to solve this problem. For example, the synthesis of PI derived from 3,3 ′ ,4,4 ′ -biphenyltetracarboxylic dianhydride and CHDA needed a short heating period to dissolve the poly(amic acid) salt.…”

“…In order to overcome the drawback of deep coloration of PIs, which is caused by intra‐ and intermolecular charge transfer interactions, many structural modification strategies have been utilized . The most effective approach is to use aliphatic tetracarboxylic dianhydrides or aliphatic diamines, which would enlarge the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and shift the absorption wavelength from the visible region to the ultraviolet (UV) region . For the former, there are many reports focusing on semi‐aromatic PIs derived from alicyclic dianhydrides with different ring sizes .…”