Kinetic study of low‐temperature imidization of poly(amic acid)s and preparation of colorless, transparent polyimide films

Yu, Hwan‐Chul; Jung, Jaewoo; Choi, Ju Chan; Chung, Chan‐Moon

doi:10.1002/pola.28013

Cited by 49 publications

(38 citation statements)

References 40 publications

(51 reference statements)

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“…The structural factors that can improve the thermal stability of polymer films often reduce the optical properties of the films at the same time, and vice versa. Thus, it is a changeling research topic to develop polymer optical films with both of excellent thermal stability and good optical transparency [5][6][7].In recent years, the research progress of colorless and transparent polyimide (CPI) films has attracted great attention in the research and development of high performance polymer optical films [8][9][10]. Based on the previous decades of research on the origination of coloration in traditional all-aromatic PI films, the researchers revealed many effective procedures to prohibit the formation of intra-or intermolecular charge transfer complexes (CTC) between the electron-donating diamine moiety and the electron-accepting dianhydride moiety so as to improve the optical transparency of the PI films [11][12][13].…”

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confidence: 99%

Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

Jiang

Wang

et al. 2020

Polymers

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Semi-alicyclic colorless and transparent polyimide (CPI) films usually suffer from the high linear coefficients of thermal expansion (CTEs) due to the intrinsic thermo-sensitive alicyclic segments in the polymers. A series of semi-alicyclic CPI films containing rigid-rod amide moieties were successfully prepared in the current work in order to reduce the CTEs of the CPI films while maintaining their original optical transparency and solution-processability. For this purpose, two alicyclic dianhydrides, hydrogenated pyromellitic anhydride (HPMDA, I), and hydrogenated 3,3',4,4'-biphenyltetracarboxylic dianhydride (HBPDA, II) were polymerized with two amide-bridged aromatic diamines, 2-methyl-4,4'-diaminobenzanilide (MeDABA, a) and 2-chloro-4,4'-diaminobenzanilide (ClDABA, b) respectively to afford four CPI resins. The derived CPI resins were all soluble in polar aprotic solvents, including N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). Flexible and tough CPI films were successfully prepared by casing the PI solutions onto glass substrates followed by thermally cured at elevated temperatures from 80 • C to 250 • C. The MeDABA derived PI-I a (HPMDA-MeDABA) and PI-II a (HBPDA-MeDABA) exhibited superior optical transparency compared to those derived from ClDABA (PI-I b and PI-II b ). PI-I a and PI-II a showed the optical transmittances of 82.3% and 85.8% at the wavelength of 400 nm with a thickness around 25 µm, respectively. Introduction of rigid-rod amide moiety endowed the HPMDA-PI films good thermal stability at elevated temperatures with the CTE values of 33.4 × 10 −6 /K for PI-I a and 27.7 × 10 −6 /K for PI-I b in the temperature range of 50-250 • C. Comparatively, the HBPDA-PI films exhibited much higher CTE values. In addition, the HPMDA-PI films exhibited good thermal stability with the 5% weight loss temperatures (T 5% ) higher than 430 • C and glass transition temperatures (T g ) in the range of 349-351 • C.The polymeric optical films with high thermal stability, high dimensional stability at elevated temperatures, high optical transparency, and high tensile properties are highly desired in modern optoelectronic areas, such as substrates or covering windows for flexible active matrix organic light-emitting diodes (AMOLED) devices, substrates for organic photovoltaic (OPV) solar cells, and so on [1][2][3]. Conventional polymeric optical films, such as polyolefin and polyester films usually suffer from the poor thermal and dimensional stability while the standard high-temperature resistant polymer films, such as the wholly aromatic polyimide (PI) films often exhibit highly colored appearance and poor optical transparency in the visible light region [4]. That is to say, the molecular structure factors that affect the optical and thermal properties of polymer films are usually contradictory. The structural factors that can improve the thermal stability of polymer films often reduce the optical properties of the films at the same time, and vice versa. Thus, it is a changeling research topic to dev...

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confidence: 99%

Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

Jiang

Wang

et al. 2020

Polymers

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“…This is because the compatibility of PI and PVDF is less than that of PAA and PVDF. With increasing reaction temperature, the degree of imidization increased . Therefore, the higher reaction temperature can lead to the accumulation of fillers when the PVDF content is very high.…”

Section: Resultsmentioning

confidence: 95%

Effect of Reaction Temperature on the Properties of Polyimide Dielectric Composites

Mao

Zhang

et al. 2019

ChemistrySelect

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Polymer dielectric composites are fabricated by blending polyimide (PI) with poly(vinylidene fluoride) (PVDF) base on different temperature conditions. The dielectric and thermal properties of the composites are studied. Experimental results indicate that the dielectric properties of the composites are enhanced by increasing the reaction temperature, while all the resulted composites exhibit excellent thermal stability. Specifically, the sample showing optimized dielectric properties can be obtained at a reaction temperature of 50°C.

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“…The results also proved the successful imide conversion from amic acid groups. The degree of imidization can be quantitatively determined by the ratio of absorbance of imide C–N at 1370 cm −1 to that of C=C stretching at 1513 cm −1 [ 40 ]. All the values calculated by I 1370 / I 1513 were more than 99% for these semi-alicyclic PIs.…”

Section: Resultsmentioning

confidence: 99%

Preparation and Characterization of Semi-Alicyclic Polyimides Containing Trifluoromethyl Groups for Optoelectronic Application

et al. 2020

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Transparent polyimides (PI) films with outstanding overall performance are attractive for next generation optoelectronic and microelectronic applications. Semi-alicyclic PIs derived from alicyclic dianhydrides and aromatic diamines have proved effective to prepare transparent PIs with high transmittance. To optimize the combined properties of semi-alicyclic PIs, incorporating bulky trifluoromethyl groups into the backbones is regarded as a powerful tool. However, the lack of fundamental understanding of structure–property relationships of fluorinated semi-alicyclic PIs constrains the design and engineering of advanced films for such challenging applications. Herein, a series of semi-alicyclic PIs derived from alicyclic dianhydrides and trifluoromethyl-containing aromatic diamines was synthesized by solution polycondensation at high temperature. The effects of alicyclic structures and bulky trifluoromethyl groups on thermal, dielectric and optical properties of PIs were investigated systematically. These PI films had excellent solubility, low water absorption and good mechanical property. They showed high heat resistance with Tg in the range of 294–390 °C. It is noted that tensile strength and thermal stability were greatly affected by the rigid linkages and alicyclic moieties, respectively. These films exhibited obviously low refractive indices and significantly reduced dielectric constants from 2.61 to 2.76, together with low optical birefringence and dielectric anisotropy. Highly transparent films exhibited cutoff wavelength even as low as 298 nm and transmittance at 500 nm over 85%, displaying almost colorless appearance with yellowness index (b*) below 4.2. The remarkable optical improvement should be mainly ascribed to both weak electron-accepting alicyclic units and bulky electron-withdrawing trifluoromethyl or sulfone groups. The present work provides an effective strategy to design molecular structures of optically transparent PIs for a trade-off between solution-processability, low water uptake, good toughness, high heat resistance, low dielectric constant and excellent optical transparency.

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Kinetic study of low‐temperature imidization of poly(amic acid)s and preparation of colorless, transparent polyimide films

Cited by 49 publications

References 40 publications

Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

Reduced Coefficients of Linear Thermal Expansion of Colorless and Transparent Semi-Alicyclic Polyimide Films via Incorporation of Rigid-Rod Amide Moiety: Preparation and Properties

Effect of Reaction Temperature on the Properties of Polyimide Dielectric Composites

Preparation and Characterization of Semi-Alicyclic Polyimides Containing Trifluoromethyl Groups for Optoelectronic Application

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