Photophysical processes in aromatic polyimides. Studies with model compounds

Hasegawa, Masatoshi; Shindo, Yoichi; Sugimura, Tokuko; Ohshima, Shigeru; Horie, Kazuyuki; Kochi, Masakatsu; Yokota, Rikio; Mita, Itaru

doi:10.1002/polb.1993.090311118

Cited by 79 publications

(96 citation statements)

References 20 publications

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“…[1][2][3][4][5] We have already achieved the synthesis of nearly colorless polyimides using dianhydrides with polyalicyclic structures. [6][7][8] Moreover, we reported entirely colorless polyimides prepared from a dianhydride with a bicyclo[2.2.1]heptane structure and aromatic diamines, although it was essential that a mixture of triphenylphosphite and pyridine (TPP/Py) was added during the course of the polymerization process.…”

Section: Introductionmentioning

confidence: 99%

Optical Properties of Polyalicyclic Polyimides.

Matsumoto

Feger

1998

J. Photopol. Sci. Technol.

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Fully imidized and solvent soluble polyimide films with a polyalicyclic structure were prepared from bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic 2,3:5,6-dianhydrides and aromatic diamines. The optical properties such as optical transparency and refractive indices have been evaluated. These films were entirely colorless, and the normalized transparencies in the visible region were over 86%. The films remained colorless and transparent up to 300°C when heated in air, and 400°C in N2. The polyimides had an average refractive index range of 1.599 to 1.617. The birefringencies of the BAB-based polyimides were nearly zero.

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Section: Introductionmentioning

confidence: 99%

Optical Properties of Polyalicyclic Polyimides.

Matsumoto

Feger

1998

J. Photopol. Sci. Technol.

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“…(73, 14) We found that a new absorption band appeared in die longer wavelength region upon blending of PI(BPDA/CHDA) (CHDA: trans 1,4-cyclohexyldiamine) with P1(DMCDA/PDA) (DMCDA: 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride) which are both Pis possessing no CT character as shown in Figure 4. Thus, for the blended PI system an intermolecular donor-acceptor interaction was demonstrated from die results in Figure 4.…”

Section: Results and Discussion Donor-acceptor Alternative Sequence Imentioning

confidence: 92%

Structure, Properties, and Intermolecular Charge Transfer of Polyimides

Hasegawa

Ishii

Matano

et al. 1995

ACS Symposium Series

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The presence of intermolecular donor-acceptor interaction in solid state aromatic polyimides (PIs) was confirmed by spectroscopic means. It was found that the thermal expansion coefficient is closely associated not only with the degree of in-plane orientation, but also with the degree of molecular stacking. These two factors influence each other, and are not completely independent. The intermolecular CT fluorescence spectra were a sensitive reflection of the molecular stacking process. Dynamic mechanical measurements of PIs suggested that the CT complexes probably function as physical crosslinks.Aromatic polyimides (Pis), especially those possessing a rigid (linear) polymer backbone, e.g., PI(BPDA/PDA) (BPDA: 3,4,3\4 f ,-biphenyltetracarboxylic dianhydride, PDA: /?-phenylenediamine), show properties depending strongly on the cure method (chemical and thermal), thermal imidization conditions (final cure temperature and heating rate), presence of substrate, and film thickness. This is attributed to the difference of the degree of molecular orientation and molecular stacking which are closely related with molecular mobility during thermal cure of polyamic acid (PAA). The aim of the work is to elucidate the presence and contribution of intermolecular charge-transfer (CT) interaction on various physical properties and to examine the relationship between physical properties and the structures of molecular aggregates. The intermolecular charge-transfer (CT) fluorescence is useful as an indicator of the degree of PI chain packing(I-i) and the miscibility of PI/PI binary blends. (4) Recently, Okabe et al. (5) reported that a PI derived from a polyamic acid ester (PAE) has a thermal expansion coefficient (TEC) higher than the PI made from the corresponding PAA. The present paper also describes the difference of molecular aggregation structure between Pis from PAA and PAE, characterized by the intrinsic intermolecular CT fluorescence(!,3) and the dichroic absorption spectra measured at a tilt angle for a rigid-rod dye dispersed in PI film. (6) EXPERIMENTAL SECTION Materials. PAAs were polymerized by adding equimolar amounts of dianhydride powder into a iV,N-dimethylacetamide (DMAc) solution of diamine at room

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“…For several model compounds, the Stern-Volmer analysis were Φ ( (385nm) = kf /(kf + k d + k isc + k CT ) <10" 4 (2)…”

Section: Photochemistry Of Benzophenone-typementioning

confidence: 99%

Photophysics, Photochemistry, and Intramolecular Charge Transfer of Polyimides

Hasegawa

Shindo

Sugimura

1995

ACS Symposium Series

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Photophysical properties of a biphenyl-type polyimide (PI) were modeled by measuring the ultraviolet-visible absorption, emission spectrum and lifetime of its model compounds in dilute solution at room temperature and 77 K. On the basis of a photophysical model, the rate constant of the intramolecular charge-transfer (CT) process in the excited state of the biphenyldiimide model compound was estimated to be more than 5x10 11 s -1 . The relationship between the intramolecular CT and photoreaction, i.e., the photo-induced hydrogen abstraction for a benzophenone-containing PI, was discussed on the basis of the photochemical kinetic parameters for its model compounds, determined by the Stern-Volmer analysis. A relation between the intramolecular CT character of the model compounds and the kinetic parameters led to the postulation of a photophysical mechanism in which intersystem crossing followed by the hydrogen abstraction competes with the intramolecular CT process followed by effective deactivation.Polyimide precursor, polyamic acids (PAA) are generally polymerized from aromatic dianhydride and aromatic diamine. The reaction proceeds through CT interaction between dianhydride as an electron acceptor and diamine as a donor.(i) It has been believed that yellow color of model compound crystals(2) and films(3) of aromatic Pis such as KAPTON results from the CT interaction. However, these systems include necessarily contribution of both intra-and intermolecular interactions. The aim of this work is to elucidate the presence of CT interactions in aromatic Pis and to examine relationship between the intramolecular CT and photophysical(4) and photochemical(5-8) properties of Pis. We focus on the model compound systems in dilute solution which precludes intermolecular interactions.A biphenyl-type PI was selected for photophysical studies because the films of polypyromellitimides are relatively nonfluorescent.(9,10) For photoreaction studies, a benzophenone-type PI was chosen. This PI is known to be useful as a thermally stable photoresist material. Upon uv-irradiation the triplet state of the benzophenonediimide unit in the PI main chain, formed by intersystem crossing, abstracts intermolecularly hydrogen atom from the adjacent alkyl groups, followed 0097-6156/95/0614-0379$12.00/0

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Photophysical processes in aromatic polyimides. Studies with model compounds

Cited by 79 publications

References 20 publications

Optical Properties of Polyalicyclic Polyimides.

Optical Properties of Polyalicyclic Polyimides.

Structure, Properties, and Intermolecular Charge Transfer of Polyimides

Photophysics, Photochemistry, and Intramolecular Charge Transfer of Polyimides

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