In-plane orientation of polyimide chains induced by thermal imidization.

Hasegawa, Masatoshi; Matano, Takafumi; Shindo, Yoichi; Sugimura, Tokuko

doi:10.2494/photopolymer.7.275

Cited by 5 publications

(5 citation statements)

References 5 publications

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“…The present paper first describes a method for evaluating the degree of in-plane molecular orientation of various PAA and PI chains (from rod-like to flexible) by measuring a visible dichroic spectrum of a rod-like dye dispersed in the matrices − and focuses on the mechanism of spontaneous orientation of the chain axis. In addition, the orientation of the phthalimide molecular plane with respect to the film plane, estimated by polarized infrared spectroscopy, and structural changes upon stepwise thermal annealing are also described.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Molecular Orientation of Polyimides Induced by Thermal Imidization. 2. In-Plane Orientation

et al. 1996

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The degree of in-plane molecular orientation of various polyimides (PIs) and their precursors, poly(amic acid)s (PAAs), were estimated by measuring the visible dichroic absorption at an incidence angle for a rod-like dye (perylenediimide, PEDI) dispersed in the matrices. The effects of PI chain structure, film thickness, heating rate, and residual solvent on a spontaneous in-plane orientation phenomenon were examined to fully understand the mechanism. All PAA films cast on a substrate showed the low degrees of in-plane orientation of the chain axis, nearly independent of the chain structure. Upon thermal imidization of the PAA films adhered on a substrate, a striking spontaneous in-plane orientation behavior was observed for some PI systems with rigid chains; in contrast to that, some flexible PI systems showed no spontaneous behavior. Cure of the PAA films adhered on a substrate induced the spontaneous orientation even if the films were considerably thick (∼50 μm); in contrast to that, the cure of the free-standing thick film did not. However, upon cure of the free-standing thin films (∼10 μm), the spontaneous orientation behavior was observed. For rigid PI systems in which interchain stacking preferentially occurs, thermal cure of the PAA films on a substrate forms liquid-crystal-like highly oriented regions, and simultaneously, apparent stretching (due to constraint of film contraction during imidization) promotes the molecular orientation further. The mechanism is closely associated with a “cooperative effect” in which the neighboring chains enhance the molecular orientation of each other during cure. In addition, structural changes (orientations of the chain axis and a molecular plane and molecular packing) upon stepwise annealing were followed. Polarized infrared absorption spectra measured at an incidence angle demonstrated that the phthalimide molecular plane in the PI film on a silicon wafer aligns somewhat parallel to the film plane, but no significant orientational and conformational changes occurred upon stepwise annealing.

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Section: Introductionmentioning

confidence: 99%

Spontaneous Molecular Orientation of Polyimides Induced by Thermal Imidization. 2. In-Plane Orientation

et al. 1996

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“…PAA(s-BPDAIODA) has a sharp exthothermic peak at 300°C due to precrystallization in the DSC thermogram, whereas PAA(a-BPDA/ ODA) does not. In addition, the film densities of the latter much lower than those of the former (see Fig.4) indicate the lower degree of We found that s-BPDA/PDA chains highly align spontaneously parallel to the film plane through on-substrate cure or bifix cure and that the degree of in-plane orientation depends strongly on film thickness in the case of free-standing cure [7,8,10] PI(a-BPDA/PDA) film (18 µm thick) showed TEC = 9.7 ppm K 1 close to that (8.8 ppm K1) of PI(s-BPDA/PDA) film (17 i.m thick) when both were cured in free-standing state upon 200°C for 3 h + 350°C for 1 h.…”

Section: Introductionmentioning

confidence: 79%

“…For another example, PI(PMDA/PDA) film cured at 350°C has no anhydride group, but it is very brittle. a kind of molecular strain stored in polymer chains such as a bond angle distortion may be related to film brittleness.Dynamic mechanical properties of a-and s-BPDA/PDA polyimide films.s-BPDA/PDA shows a character that the polymer chains spontaneously aligns parallel to the film plane during thermal imidization, and the degree of in-plane orientation depends strongly on film thickness and constraint of the films (cure in free-standing state, in a frame, or on a substrate) [7,8,10]. The degree of in-plane orientation significantly influences the dynamic mechanical properties.…”

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confidence: 99%

Structure and Properties of Novel Asymmetric Biphenyl Type Polyimides.

Hasegawa

Sensui

Shindo

et al. 1996

J. Photopol. Sci. Technol.

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Asymmetric biphenyl type polyimides (PI) were prepared by thermal imidization of polyamic acids (PAA) derived from 2,3,3',4'biphenyltetracarboxylic dianhydride (a-BPDA) and p-phenylenediamine (PDA) or 4,4'-oxydianiline (ODA). The degrees of molecular orientation, film densities, and dynamic mechanical properties of these PIs were compared with those of familiar PIs based on symmetric 3,4,3',4'biphenyltetracazboxylic dianhydride (s-BPDA). PI(a-BPDA/PDA) cured at 350°C showed a Tg close to that of PI(s-BPDA/PDA) prepared under the same condition in spite of the bent chain structure of the former. Comparison of the PIs cured at 400°C manifested that PI(a-BPDA/PDA) has a Tg at 410°C (abrupt decrease in E') whereas PI(s-BPDA/PDA) show no distinct Tg. Similar result was also observed for the ODA systems. The unexpectedly high Tgs of a-BPDA-based PIs were explained in terms of the restricted conformational change around the phenyl-phenyl bond in the a-BPDA unit. The difference of the E' decrement at the Tg for both type of PIs are probably attributed to the difference of the intensity of intermolecular interactions. In PI(a-BPDA/ PDA) thin film cured on a substrate, the segments unexpectedly align slightly to the film plane.

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“…The incidence angle was adjusted on die basis of the refractive indices. (6)(7)(8) We defined/= (l-D)/(l-£>0) as an in-plane orientation parameter, where the dichroic ratio D is the absorbance ratio [at peak wavelength (ca. 535 nm) of PEDI] of the linearly polarized lights parallel (Ppolarized light) and perpendicular (5-polarized light) to the incidence plane, i.e., (Aρ /Ash and Do (= cos 2 a) is the dichroic ratio for complete in-plane orientation (two-dimensionally random).…”

Section: Physical Properties Affected By In-plane Molecular Orientatimentioning

confidence: 99%

“…The detailed procedure is described in ref. [6][7][8]. Film density was measured using a density gradient column composed of xylene-CCU mixtures.…”

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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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In-plane orientation of polyimide chains induced by thermal imidization.

Cited by 5 publications

References 5 publications

Spontaneous Molecular Orientation of Polyimides Induced by Thermal Imidization. 2. In-Plane Orientation

Spontaneous Molecular Orientation of Polyimides Induced by Thermal Imidization. 2. In-Plane Orientation

Structure and Properties of Novel Asymmetric Biphenyl Type Polyimides.

Structure, Properties, and Intermolecular Charge Transfer of Polyimides

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