Structural Evolution of Macromolecular Chain During Pre-imidization Process and Its Effects on Polyimide Film Properties

Lin, Daolei; Liu, Yingzi; Jia, Ziqi; Qi, Shengli; Wu, Dezhen

doi:10.1021/acs.jpcb.0c05146

Cited by 27 publications

(13 citation statements)

References 47 publications

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“…Another factor that may have an effect is the presence of impurities (e.g., oxidized non-reacted diamines) [34]; however, for wholly aromatic polyimides such as PMDA-ODA, it is widely regarded that the coloration is predominantly related to increases in charge transfer interactions [37][38][39][40][41][42][43]. Since CTC formation increases with curing temperature, the color intensity increases concomitantly [44]. Spectroscopy has been used by researchers to track the optical properties of polyimide samples [45][46][47].…”

Section: Resultsmentioning

confidence: 99%

A Universal Study on the Effect Thermal Imidization Has on the Physico-Chemical, Mechanical, Thermal and Electrical Properties of Polyimide for Integrated Electronics Applications

et al. 2022

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Polyimides (PI) are a class of dielectric polymer used in a wide range of electronics and electrical engineering applications from low-voltage microelectronics to high voltage isolation. They are well appreciated because of their excellent thermal, electrical, and mechanical properties, each of which need to be optimized uniquely depending on the end application. For example, for high-voltage applications, the final polymer breakdown field and dielectric properties must be optimized, both of which are dependent on the curing process and the final physico-chemical properties of PI. The majority of studies to date have focused on a limited set of properties of the polymer and have analyzed the effect of curing from a physicochemical-, mechanical- or electrical-centric viewpoint. This paper seeks to overcome this, unifying all of these characterizations in the same study to accurately describe the universal effect of the cure temperature on the properties of PI and at an industrial processing scale. This paper reports the widest-ranging study of its kind on the effect that cure temperature has on the physico-chemical, mechanical, thermal and electrical properties of polyimide, specifically poly (pyromellitic dianhydride-co-4, 4′-oxydianiline) (PMDA/ODA). The optimization of the cure temperature is accurately studied not only regarding the degree of imidization (DOI), but also considering the entire physical properties. Particularly, the analysis elucidates the key role of the charge–transfer complex (CTC) on these properties. The results show that while the thermal and mechanical properties improve with both DOI and CTC formation, the electrical properties, particularly at high field conditions, show an antagonistic behavior enhancing with increasing DOI while degrading at higher temperatures as the CTC formation increases. The electrical characterization at low field presents an enhancement of the final PI properties likely due to the DOI. On the contrary, at high electric field, the conductivity results show an improvement at an intermediate temperature emphasizing an ideal compromise between a high DOI and PI chain packing when the thermal imidization process is performed over this equilibrium. This balance enables maximum performance to be obtained for the PI film with optimized electrical properties and, overall, optimal thermal and mechanical properties are achieved.

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Section: Resultsmentioning

confidence: 99%

A Universal Study on the Effect Thermal Imidization Has on the Physico-Chemical, Mechanical, Thermal and Electrical Properties of Polyimide for Integrated Electronics Applications

et al. 2022

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“…The aggregation structure of the PI films was analyzed by the X-ray diffraction (XRD), as shown in Figure 3b. A wide diffraction peak appears at 10-20 • in the XRD patterns for TIPI and CIPI-w films, indicating a typical amorphous structure [40]. The typical characteristic peak is located at 13.7 • , which is indexed to the corresponding (101) plane of PI (PDF#54-2400).…”

Section: Structure and Properties Of Pi Filmsmentioning

confidence: 99%

Highly Thermal Conductive Graphite Films Derived from the Graphitization of Chemically Imidized Polyimide Films

Sun

Wang

et al. 2022

Nanomaterials

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With the large-scale application and high-speed operation of electronic equipment, the thermal diffusion problem presents an increasing requirement for effective heat dissipation materials. Herein, high thermal conductive graphite films were fabricated via the graphitization of polyimide (PI) films with different amounts of chemical catalytic reagent. The results showed that chemically imidized PI (CIPI) films exhibit a higher tensile strength, thermal stability, and imidization degree than that of purely thermally imidized PI (TIPI) films. The graphite films derived from CIPI films present a more complete crystal orientation and ordered arrangement. With only 0.72% chemical catalytic reagent, the graphitized CIPI film achieved a high thermal conductivity of 1767 W·m−1·K−1, which is much higher than that of graphited TIPI film (1331 W·m−1·K−1), with an increase of 32.8%. The high thermal conductivity is attributed to the large in-plane crystallite size and high crystal integrity. It is believed that the chemical imidization method prioritizes the preparation of high-quality PI films and helps graphite films achieve an excellent performance.

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“…NPT ensemble and NVT ensemble were employed to obtain the final equilibrium model. [34][35][36] The PMDA/ODA orientation models of molecular chains arranged along the drafting direction were constructed by applying tensile force in the X-axis direction of the amorphous model based on our previous work, [37] and certain pressure is applied in the Y-and Z-axis directions to ensure that the density of the model is within a reasonable range during the drafting process. The drafting rate of the orientation models were regulated by applying drafting strengths of 0.20, 0.25, 0.30, and 0.35 GPa in the X-axis direction, respectively.…”

Section: Molecular Simulation Detailsmentioning

confidence: 99%

Clarifying the Effect of Drafting Conditions on Structure and Properties of Polyimide Fibers at Molecular Dynamic Level

Lin

Jiang

et al. 2022

Macro Theory & Simulations

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A series of pyromellitic dianhydride/4,4′-oxydianiline orientation models are constructed by molecular dynamic simulation, and the effects of drafting rate, drafting temperature, and imidization degree on structure and mechanical properties of polyimide fibers are studied. The high drafting rate is conducive to the orientation of molecular chains along the axis, but it is easy to form defects inside of the fibers, so the tensile modulus of the orientation model at a draft ratio of 6 is decreased from 21.6 to 9.8 GPa with increasing the drafting rate. The high drafting temperature reduced the intermolecular interaction, which is not conducive to the orientation of the molecular chain along the axis, the tensile modulus of orientation models at a draft ratio of 6 decreased from 21.6 to 11.7 GPa with the drafting temperature increasing from 298 to 598 K. Besides, the molecular chains of PI fibers drawn from the high imidization degree are arranged more regularly along the axis due to the PI units have greater rigidity than the polyamic acid units. This work provides guidance for the optimization of PI fibers heat-drafting process from the perspective of molecular chain conformational evolution.

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Structural Evolution of Macromolecular Chain During Pre-imidization Process and Its Effects on Polyimide Film Properties

Cited by 27 publications

References 47 publications

A Universal Study on the Effect Thermal Imidization Has on the Physico-Chemical, Mechanical, Thermal and Electrical Properties of Polyimide for Integrated Electronics Applications

A Universal Study on the Effect Thermal Imidization Has on the Physico-Chemical, Mechanical, Thermal and Electrical Properties of Polyimide for Integrated Electronics Applications

Highly Thermal Conductive Graphite Films Derived from the Graphitization of Chemically Imidized Polyimide Films

Clarifying the Effect of Drafting Conditions on Structure and Properties of Polyimide Fibers at Molecular Dynamic Level

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