Cause of the discolouration of aromatic polyimides

Bikson, Benjamin; Freimanis, Ya. F.

doi:10.1016/0032-3950(70)90279-0

Cited by 15 publications

(16 citation statements)

References 2 publications

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“…The diamines labeled with the compound numbers are shown in Figure 1. The orders of (a) was derived from the spectra in Figure 6, and those of(b), (c), and (d) are prepared from the data reported by Bikson, 9 St. Clair, 13 and Noda. 20 It is noteworthy that there is no inconsistency in the orders of color intensity, and the polyimides derived from BTDA and 6FDA always have deeper and lighter colors, respectively, than those expected from their electron-accepting properties.…”

Section: Color Intensity Of Polyimides and Electron-accepting Propertmentioning

confidence: 99%

“…Figure 3 shows arrangements of diamine moieties in order of the color intensity of polyimides from deep to pale when the dianhydride structures are fixed. These were prepared from the data reported by Bikson, 9 St. Clair, 13 and Noda. 2° For the diamines shown in Figures 3(a) and (b ), the color intensities of the polyimides were elucidated from the Ao observed in their absorption spectra.…”

Section: Color Intensity Of Polyimides and Electron-donatingmentioning

confidence: 99%

“…This fact indicates that the fluorination of source materials does not necessarily lead to colorless polyimides. If the coloration of polyimide films can be predicted from the properties of their source materials, it should be helpful for the development of polyimides used for optical applications.Bikson et al 9 showed that the color intensity of polyimides is related to the structure of the monomers from which they are derived. They mentioned that the dianhydride structure is more influential in determining the color intensity of polyimides than the diamine structure, and they attributed this to the extent of conjugation at the 5-membered imide ring.…”

mentioning

confidence: 99%

“…Bikson et al 9 showed that the color intensity of polyimides is related to the structure of the monomers from which they are derived. They mentioned that the dianhydride structure is more influential in determining the color intensity of polyimides than the diamine structure, and they attributed this to the extent of conjugation at the 5-membered imide ring.…”

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confidence: 99%

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Coloration of Aromatic Polyimides and Electronic Properties of Their Source Materials

Ando

Matsuura

Sasaki

1997

Polym J

273

209

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ABSTRACT:The relationships between the color intensities of polyimide films and the electronic properties of their source materials-aromatic diamines and aromatic tetracarboxylic dianhydrides-are discussed. The arrangement of the diamine moieties in order of color intensity of polyimides shows fairly good agreement with the order of the electron-donating properties of the diamines estimated from 15 N NMR chemical shifts (bN). On the other hand, the arrangement of the dianhydrides moieties in order of color intensity of polyimides agrees with the order of the electron-accepting properties of the dianhydrides estimated from experimental and calculated electron affinity (EA) although systematic inconsistencies are observed for the dianhydrides having-CF 3 groups and a benzophenone carbonyl group. These results are consistent with the formation of charge transfer complex (CTC) and indicate that the electron-donating properties of diamines and electron-accepting properties of dianhydrides are retained to a significant extent even in polyimide molecular chains. KEY WORDSPolyimide / Coloration / Charge Transfer Complex / Dianhydride / Diamine / Nuclear Megnetic Resonance Chemical Shift / MNDO-PM3 / Optical transparency of polyimide films is of special importance in some applications such as flexible solar radiation protectors, 1 orientation films in liquid crystal display devices, 2 optical waveguides for communication interconnects, 3 and optical half-waveplates for planar lightwave circuits. 4 However, most of the conventional polyimide films always show considerable coloration ranging from pale yellow to deep brown. Rogers 5 first reported that optically transparent and colorless polyimides can be synthesized from a dianhydride and a diamine that have hexafluoroisopropyridene (-C(CF 3 ) 2-) groups. We have reported that the fluorinated polyimides derived from 2,2' -bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) exhibit excellent properties needed for optical applications. 6 In particular, the polyimide derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and TFDB show no color, high transparency in the visible region, and low optical transmission losses in the near-infrared region as well as low dielectric constants, low refractive indices, and low water absorption. The idea that fluorination of dianhydride and diamine moieties give colorless polyimides are widely accepted. On the other hand, we have recently reported the first synthesis of perfluorinated polyimides that have very high optical transparency over the entire range of optical communication wavelengths (1.0--1.7 µm) and high glass transition temperatures over 300°C. 7 • 8 Despite the high fluorination of the diamine and dianhydride, the perfluorinated polyimides show considerable coloration ranging from orange to brown. This fact indicates that the fluorination of source materials does not necessarily lead to colorless polyimides. If the coloration of polyimide films can be predicted from the properties of their source materia...

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Section: Color Intensity Of Polyimides and Electron-accepting Propertmentioning

confidence: 99%

Section: Color Intensity Of Polyimides and Electron-donatingmentioning

confidence: 99%

mentioning

confidence: 99%

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Coloration of Aromatic Polyimides and Electronic Properties of Their Source Materials

Ando

Matsuura

Sasaki

1997

Polym J

273

209

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“…In addition, generally, polyimides have intrisically yellowish coloration problem related to the extent of diimide fragment conjugation. 4 Moreover, the pretilt angle of LC molecules, required for obtaining a defect-free alignment and improving the electro-optical performance, on the polyimide layer surfaces cannot be easily controlled using the rubbing technique by controlling the rubbing condition such as rubbing depth and/or number of rubbings. Poly(arylene ether sulfone) (PAES) and its derivatives synthesized by the step-growth polymerization of dihydroxy and dihalo monomers, one of the engineering thermoplastics, are widely used in the electronic field due to their high thermal stability, excellent mechanical and electrical properties, as well as their resistance to thermo-oxidation and hydrolysis by acids and bases.…”

Section: Introductionmentioning

confidence: 99%

Liquid crystal alignment behavior on sulfonated poly(arylene ether sulfone) films

et al. 2015

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Synthesis and properties of novel colorless and thermostable polyimides containing cross‐linkable bulky tetrafluorostyrol pendant group and organosoluble triphenylmethane backbone structure

Yan

Zhang

et al. 2020

Journal of Polymer Science

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A colorless and high temperature resistant fluorinated polyimide (PI) film based on a novel cross‐linkable diamine monomer 4,4′‐diamino‐4″‐(2,3,5,6‐tetrafluoro‐4‐ethylenephenoxy) triphenylmethane (DFPTM) was successfully prepared. The special triphenylmethane backbone and the bulky tetrafluorostyrol pendant group in DFPTM gave the PI material eximious solubility in organic solvents, high tensile properties, good thermal stability, and excellent optical transparency (cutoff wavelength for 331 nm and light transmittance above 94% at 450 nm). Furthermore, the styryl could initiate self‐crosslinking reaction to form a dense three‐dimensional network structure by thermal curing. Hence, the cross‐linked PI film showed superior combination property (including excellent resistance to solvents). It's Tg increased by 57.1–306.0°C, the 5% thermal weight‐loss temperature improved by 10.2% to 500.0°C, and the tensile strength enhanced by 17.5% to 39.7 MPa. Moreover, after thermal curing, the cross‐linked PI attained a lower elongation at break from 8.1 to 3.9%, and the thermal expansion coefficient reduced from 82.2 to 68.8 ppm/°C without obvious loss of optical transparency (cutoff wavelength for 347 nm and light transmittance remained 93.0% at 450 nm).

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Cause of the discolouration of aromatic polyimides

Cited by 15 publications

References 2 publications

Coloration of Aromatic Polyimides and Electronic Properties of Their Source Materials

Coloration of Aromatic Polyimides and Electronic Properties of Their Source Materials

Liquid crystal alignment behavior on sulfonated poly(arylene ether sulfone) films

Synthesis and properties of novel colorless and thermostable polyimides containing cross‐linkable bulky tetrafluorostyrol pendant group and organosoluble triphenylmethane backbone structure

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