Design and synthesis of organosoluble and transparent polyimides containing bulky substituents and noncoplanar structures

Abstract

A new diamine monomer, 3,3 0 -diisopropyl-4,4 0 -diaminophenyl-4 00 -phenyltouene, was designed, synthesized, and then polymerized with five commercial dianhydrides to obtain a series of novel polyimides via a one-step method. The obtained polymers showed excellent solubility in most common solvents, even in low-boiling solvents, such as chloroform, dichloromethane, and tetrahydrofuran. They exhibited a high thermal stability with the glass-transition temperature in the range 262-3188C and 10% weight loss temperatures in the range 464-4888C under a nitrogen atmospheres. Meanwhile, these polymer films also displayed a high optical transparency with a cutoff wavelength in the range 305-365 nm; prominent mechanical properties with a tensile strength of 65.6-94.9 MPa, a Young's modulus of 1.6-2.8 GPa, and an elongation at break of 9.3-13.7%; a low dielectric constant in the range of 2.91-3.18 at 1 MHz; and an outstanding hydrophobicity with a contact angle above 90.68. V C 2015 Wiley Periodicals, Inc. J.Appl. Polym. Sci. 2016, 133, 43266.

Synthesis of highly transparent and heat‐resistant polyimides containing bulky pendant moieties

“…The higher T g of PI‐6 and PI‐7 than other PIs except PI‐1 could be due to the rigid alicyclic structures in CBDA and BTA. Compared with PIs having other symmetric bulky isopropyl and biphenyl moieties, all T g values for our PIs were found to be higher by at least 50 °C …”

“…Different approaches have been reported in order to improve the transmittance and solubility of PI films, including the incorporation of flexible linkages, fluorinated structures, unsymmetrical or noncoplanar structures, alicyclic structures in the backbone and the introduction of bulky pendant substituents to the polymer chains . On the other hand, the solubility and transparency of PI films could be improved by the incorporation of flexible lineages like –O– or –S–.…”

“…Meanwhile, reduction of the conjugation and intermolecular charge transfer effect due to the bulky pendant substituents has been conducive to eliminating the deep color. For example, Huang et al reported a new aromatic diamine with bulky isopropyl and biphenyl moieties . The aromatic PIs obtained presented high transparency and excellent solubility.…”

Low‐dielectric‐constant aromatic homopolyimide and copolyimide derived from pyromellitic dianhydride, 4,4′‐oxydianiline, 2,2‐bis[4‐(4‐aminephenoxy)phenyl]propane, 1,4‐bis(4‐aminophenoxy)benzene, or 1,3‐bis(4‐aminophenoxy)benzene

“…More and more researchers have focused on synthesizing new diamine monomers and dianhydride acid monomers because fluorinated monomers cause the polyimide to have a low strength and the performance of the polyimide composites were limited to its compatibility. The side groups, hyperbranched structures, and new diamine monomers containing semifluorinated groups, isopropyl, phenyl phosphyl, and organosilicone have resulted in a large free volume and a decreased dielectric constant. However, monomers have been key in preparing low‐dielectric‐constant polyimides, whereas the previous studies reported dielectric constants from 2 to 3 because the asymmetric structures enhanced the molecular polarity and the monomers were not easily obtained; this limits their applications.…”

Incorporation of COF‐LZU‐1 into the terpolyimide matrix to obtain COF‐LZU‐1/terpolyimide composites with ultra‐low dielectric constant

“…So, the researchers have applied different post‐modification methods to reduce it to a convenient scale. Several methods such as incorporation of porous material into the polymer matrix , thermal degradation of labile graft or block chains in the polyimides , introduction of bulk fluorinated substituents into the polymer backbone , and so forth. were applied to reduce dielectric constant.…”