Photoconductivity of a Polyimide with an Alicyclic Diamine Doped with N,N,N′N′-Tetramethyl-p-phenylenediamine

Abstract

ABSTRACT:Photoconductivity of a polyimide with an alicyclic diamine [the polyimide film prepared from pyromellitic dianhydride and diaminodicyclo hexylmethane Pl(PMDA/DCHM)], and an aromatic polyimide [the polyimide film prepared from pyromellitic dianhydride and oxydianiline PI(PMDA/ODA)] was investigated by the addition of an electron donor, N,N,N' N' -tetramethyl-p-phenylenediamine (TMPD). The addition of the electron donor increased the photocurrent generation of two polyimide films by about three orders of magnitude shifting to longer wavelength by forming intermolecular charge-transfer complex in the ground state of the polyimide films. The polyimide with the alicyclic diamine doped with the electron donor showed a larger enhancement of photocurrent probably due to the existence of only intermolecular charge-transfer complex in the polyimide film, compared to the case of the aromatic polyimide having charge-transfer complex both intra-and intermolecularly. The mechanism of the enhancement of photocurrent by the addition of the electron donor would be first due to photo-absorption by the intermolecular charge-transfer complex formed between the added electron donor and pyromellitic imide unit of the polymer backbone. Under an applied field, its excitation is followed by rapid electron transfer from the donor to pyromellitic imide to produce the radical anion of the polymer and the radical cation of the donor, resulting in the photoconductivity in the bulk polyimide films.

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

“…The increase in photocurrent generation by one order of magnitude for the PI(PMDA/DCHM) film after annealing is suggested to be due to the increase in the degree of molecular packing between polymer backbone intermolecularly. 22 Both PI(PMDA/DCHM) and PI(PMDA/DMDHM) films have pyromellitic imide moiety in their polymer backbone; the only difference is that DMDHM contains two methyl substituents. The photocurrent of PI(PMDA/ DMDHM) should have been observed if photoconductivity were due to pyromellitic imide moieties in the ground or excited state.…”

“…Under the same conditions at wavelengths where the absorbance of the films were the same. 22 these conditions, almost all of the poly(amide …”

Temperature dependence of electric conduction in polyimides with main chain triphenylamine structures

“…[4][5][6]9 The electrical conduction behaviors of PMDA/ODA films have been investigated by several research groups. [10][11][12][13][14][15][16][17][18][19] Sawa et al 13 studied the electric conduction current of PMDA/ODA films at temperatures of 120-180 1C and applied electric fields of 4 À500 kV cm À1 . They concluded that the conduction in the PI films is caused by ionic hopping.…”

“…This indicates that both enhancement in the charge mobility and an increase in the number of electronic carriers in the bulk are necessary to improve the conductivity of PIs. Lee et al [17][18][19] investigated the photoconductivity of semi-aliphatic 4,4 0 -diaminodicyclohexylmethane (PMDA/DCHM) PI films. They reported that a charge-transfer complex is formed in the excited state when an optical absorption band assignable to weak intermolecular interactions is excited, and the charge-transfer complex subsequently produces charge carriers of radical cations and radical anions.…”

Absorption, Fluorescence and Thermal Properties of Transparent Polyimides Based on 2,3,5-Tricarboxycyclopentylacetic Acid Dianhydride.

“…[1] In general, polyimides (PI) are prepared by a two-step process; first, diamines react with dianhydrides in aprotic polar solvents at room temperature to give poly(amide acid)s (PAA), the precursor of polyimides; second, poly (amide acid)s are converted to polyimides by either thermal or chemical imidization. Recently, new polyimides with various functional groups which show high solvent solubility, [2][3][4] high photosensitivity, [5][6][7] and photoconductivity, [8][9][10] have been actively investigated. Although polyimides have been widely used in microelectronics and space industry, their apparent color from yellow to brown has limited their application in optical communication and liquid crystal display devices.…”