Colorless Polyimides Derived from Octahydro-2,3,6,7-anthracenetetracarboxylic Dianhydride

Abstract

A cycloaliphatic tetracarboxylic dianhydride, octahydro-2,3,6,7-anthracenetetracarboxylic dianhydride (OHADA) was synthesized to obtain novel colorless polyimides (PIs). Herein, approaches for decolorizing an OHADA prototype and simplifying the entire process are described, and a plausible steric structure for OHADA is proposed. The polyaddition of OHADA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) was unsuccessful; specifically, the reaction mixture remained inhomogeneous even after prolonged stirring. However, the modified one-pot process was applicable to the OHADA/TFMB system. The isolated PI powder form, as well as those for the other OHADA-based PIs, was highly soluble in numerous solvents and afforded a homogeneous and stable solution with a high solid content (20–30 wt%). Solution casting produced a colorless and ductile PI film with a very high glass transition temperature (Tg~300 °C). Furthermore, the OHADA/TFMB system exhibited remarkable thermal stability compared with those of the other related TFMB-derived semi-cycloaliphatic PIs. However, contrary to our expectations, this PI film did not exhibit a low linear coefficient of thermal expansion (CTE). This PI film also possessed excellent thermoplasticity, probably reflecting its peculiar steric structure. The use of an amide-containing diamine significantly enhanced the Tg (355 °C) and somewhat reduced the CTE (41.5 ppm K−1) while maintaining high optical transparency and excellent solubility.

Colorless Polyimides Derived from 5,5′-bis(2,3-norbornanedicarboxylic anhydride): Strategies to Reduce the Linear Coefficients of Thermal Expansion and Improve the Film Toughness

“…In principle, simultaneously achieving low CTE and high optical transparency is not always the trade-off. However, in fact, this issue is not easy to solve because the use of cycloaliphatic monomers to ensure film transparency often increases CTE, suggesting the importance of their steric structures in reducing the CTE of the resultant PI films [ 30 , 31 , 32 , 38 , 45 , 47 ]. On the other hand, there is the trade-off between low CTE and excellent solution processability because the molecular design for ensuring a low CTE (i.e., to enhance main-chain linearity/rigidity) often results in a significant decrease in solubility, and vice versa [ 61 , 62 ].…”

“…On the other hand, the use of OHADA resulted in a distinctly decreased T g in relation to that of the above-mentioned ultrahigh- T g PI groups (H-BTA-, CBDA-, and BNBDA-based systems), as shown in Figure 11 a, probably owing to disturbed close chain stacking, consequently weakened dipole–dipole interactions arising from a highly distorted, and non-planar steric structure of the OHADA-based diimide (OHADI) units [ 47 ].…”

“…The intense coloration of wholly aromatic PI films can be effectively eliminated by replacing either aromatic tetracarboxylic dianhydrides or aromatic diamines with aliphatic ones (usually cycloaliphatic (alicyclic) monomers) to impart heat resistance to the resultant PIs [ 18 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. Figure 1 shows the molecular structures of the typical aliphatic diamine monomers.…”

“…In contrast, when cycloaliphatic TCDAs and aromatic diamines were combined, no salt formation occurs during the polyaddition. Therefore, this type of semi-aromatic colorless PI systems has been more extensively studied [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. The structures of typical cycloaliphatic TCDAs are shown in Figure 3 .…”

Soluble Polyimides Containing Benzocyclobutene Moieties: Synthesis, Cross-Linking Behavior, and Physical and Gas Transport Properties

“…Polyimide (PI) is an organic polymer material known for its excellent overall performance. Owing to its excellent heat and chemical resistance, exceptional film-forming ability, and superior mechanical and physical properties, − it is widely used in automotive components, medical tubes, humidity sensors, fuel cells, optical films, and gas separation membranes. − In the area of gas separation, PI has attracted considerable attention because most commercial gas separation membranes are still derived from commodity polymers, for example, polysulfone and cellulose acetate, which are unsuitable for harsh industrially relevant conditions, such as high temperature and pressure. , …”