A method to break charge transfer complex of polyimide: A study on solution behavior

Abstract

Charge transfer complex strongly affects the optical transparency of polyimide film. Here, solution behavior of a polyimide derived from 3,3 0 ,4,4 0 biphenyltetracarboxylic dianhydride and 1,4-bis(3-aminopropyl)piperazine in acetic acid, chloroform, and their mixed solvents is investigated in detail by light scattering. It is found that the polyimide existed as single chains in acetic acid owing to the acid-base interaction. However, association is observed in chloroform solution because of the charge transfer complex and enhanced by increasing the solution concentration. To break the charge transfer interaction and clear the association, only a small amount of acetic acid is required to add into the chloroform solution owing to the protonation of the diamine groups, confirmed by the zeta potential measurements. Simultaneously, the associates disappear quickly after addition of acetic acid. This study will provide a novel method for preparation of high optical transparent polyimide film by simply tuning the solvent.

Insights on Light Dispersion in Semi‐Alicyclic Polyimide Alignment Layers to Reduce Optical Losses in Display Devices

“…Thus, to overcome the mentioned issues, the imidic polymer film must have high optical transparency, low refractive index, and reduced dielectric constant to enable an optimal interaction of the LC with the incident radiations. In order to improve these physical properties, many efforts were directed toward the reduction of the intra‐ and intermolecular charge transfer complex (CTC) . This can be accomplished by the introduction of low polarizable atoms or groups in the PI backbone (i.e., fluorine or aliphatic units) .…”

The Effect of End Group and Molecular Weight on the Yellowness of Polyetherimide

“…CTC is mainly responsible for the yellowness in polyimides . In PEIs, intrachain CTC forms between an electron‐withdrawing anhydride moiety and an neighboring electron‐donating amine moiety in the same chain, while interchain CTC forms between an anhydride moiety and an amine moiety in two neighboring chains (Figure S2, Supporting Information) . Two factors determine the CTC formation in PEIs: the end group type and M n .…”

“…Two factors determine the CTC formation in PEIs: the end group type and M n . First, electron‐donating groups facilitate while electron‐withdrawing groups suppress the CTC formation by altering the electron density in the chain . Therefore, for PEIs of the same M n , the yellowness increases as the end group becomes more electron‐donating (–DA < –Ph < –PA < –NH 2 ) .…”

“…Charge‐transfer complex (CTC) is mainly responsible for the yellowness of PEIs and other polyimides. In PEIs synthesized from 2,2‐bis[4‐(3,4‐dicarboxyphenoxy) phenyl] propane dianhydride (BPADA) and m ‐phenylenediamine ( m PD), the electron‐rich diamine moieties serve as electron donors and the electron‐deficient dianhydride moieties as electron acceptors.…”

Synthesis, Characterization and Film Preparation of New Co-Polyimide Based on New 3,5-Diamino- N -(Pyridin-4-Ylmethyl)benzamide, Oda and 6fda

“…[12][13][14] However, both are often limited by processing difficulties attributed to the high melting temperature and poor solubility in various organic solvents. Both problems can be explained by the existence of strong interactions due to the formation of intra-and intermolecular charge transfer complexes of the polyimides 15, 16 and to the formation of hydrogen bonds in the polyamides.…”