Transient Absorption Spectra of Photoconductive Polyimides and Their Model Compound by Picosecond Pulse Radiolysis

Abstract

Transient absorption spectra of an aromatic polyimide, PI(PMDA/ODA), and a polyimide with an alicyclic diamine, PI(PMDA/DCHM), were determined in order to investigate the main active species in the photoconductivity of the polyimide films by picosecond pulse radiolysis method. A model compound, N,N′di-n-butylpyromellitic diimide (DBPMDI), was utilized to investigate the active species of pyromellitic imide moieties in solutions of dichloromethane (DCM) and tetrahydrofuran (THF). In the aromatic polyimide film, the radical anions of the electron-accepting pyromellitic imide moieties at 660 and 720 nm and the radical cation of diphenyl ether moieties at 550 nm were determined by electron transfer from the aromatic ring to imide moieties in the polymer backbone. In the polyimide film with the alicyclic diamine, by utilizing the model system, only the radical anions of pyromellitic imide moieties could be assumed at 660 and 720 nm as the active species in the photoconductivity of the polyimide film. These active species, such as radical cations or radical anions, are expected to be the charge carriers of holes or electrons under the applied electric field, and the transport of these charge carriers would result in the photoconductivity of the polyimide films.

BPDA-PDA Polyimide: Synthesis, Characterizations, Aging and Semiconductor Device Passivation

“…Unfortunately, it is quite difficult to predict a priori the imidization temperature optimum which leads to the best electrical properties. Literature presents a large range of imidization temperature from 200 °C to 425 °C without always indicating if it corresponds to an optimum [6,[18][19][20][21][22][23]. Moreover, these works present mainly the optimization of the imidization reaction from a chemical point of view only based on qualitative infrared measurements.…”

Photoconductivity of a polyimide with an alicyclic diamine: Charge carrier photogeneration in the mixed layer packing arrangement

“…6, 17,18 To investigate the intra-or intermolecular interaction of the polyimide with the alicyclic diamine, PI(PMDA/DCHM), UV absorption spectra were observed first using a model system (CPD). Figure 2 shows absorption spectra of the model compound acid)s was converted to the polyimides, which was ascertained by IR spectroscopy.…”

“…matic hydrocarbons in aromatic amine solvents by measuring the fluorescence spectra reported Photoconduction mechanism of PI(PMDA/ by Mataga et al 39,40 They have reported that the ODA) film is well known to be due to the chargeabsorption spectra of the hydrocarbons in the transfer complex formed between pyromellitic imamines do not show any essential change, but speide moiety and diphenyl ether group in the ground cific interaction between a hydrocarbon and an state both intra-and intermolecularly. 6,17, 18 We 18 amine occurs only in the electronically excited have investigated the charge carriers in the phostate (the fluorescent state). It has been clearly toconductivity of PI(PMDA/ODA) film by using demonstrated from the relationship among the a picosecond pulse radiolysis method, reporting a frequencies of the long wavelength fluorescence, radical cation of diphenyl ether moiety at 550 nm the electron affinities of the excited-state aroand radical anions of pyromellitic imide moiety matic hydrocarbons, and the ionization potentials at 660 and 720 nm by electron transfer from the of the amines, that the interaction can be ascribed aromatic ring to imide moiety in the polymer to the charge transfer from the amine to the exbackbones.…”

“…between aromatic diamine moieties as electron donors and aromatic dianhydride moieties as electron acceptors both intra-and intermolecularly. [17][18][19][20] EXPERIMENTAL In our previous articles, 21,22 the photoconductivity of a polyimide prepared from pyromellitic Materials and Solvents dianhydride (PMDA) and 4,4 -diaminodicyclohexylmethane (DCHM), PI(PMDA/DCHM), was Pyromellitic dianhydride (PMDA) supplied by investigated and compared with that of an aro-Tokyo Kasei Co. Ltd. was purified by recrystallimatic polyimide, PI(PMDA/ODA), composed of zation in distilled acetic anhydride, and dried at PMDA and oxy-4,4-dianiline (ODA) both in the high temperature (150ЊC) under vacuum for 12 absence 21 and presence 22 of N,N,N,N-tetra-h. 4,4-Diaminodicyclohexylmethane (mixture of methyl-p-phenylenediamine (TMPD) as an elecisomers, DCHM) was supplied by Wako Pure tron donor.…”

Long-lived Intermediates in Radiation-induced Reactions of Alicyclic Polyimides Films

“…Judging from the result of pulse radioly model compounds in solution, the long-lived intermediate at 720 nm is assigned to radical anion of the electron-accepting pyromellitic imide moieties in the aromatic PI films [8]. The other peaks at 420 and 600 nm decayed simultaneously within 3 hours.…”