The synthesis and thermal, optical and electrical properties of novel aromatic–aliphatic five- and six-membered thermotropic polyimides

Schab‐Balcerzak, Ewa; Wegrzyn, Marcin; Janeczek, Henryk; Jarząbek, Bożena; Rannou, Patrice; Iwan, Agnieszka

doi:10.1080/02678292.2010.506578

Cited by 11 publications

(4 citation statements)

References 30 publications

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“…The lowest crystal–LC transition temperature was 163 °C during a heating process that originated from long siloxane units and the fluoro substituent on the mesogenic units to reduce the polymer packing interaction. This LC transition temperature was lower than those of the reported LC polyimides containing similar mesogenic units. − However, the morphology of their LC structures was not maintained at room temperature because of the crystallization during the cooling process to room temperature. Therefore, cross-linking would be a suitable method for maintaining their LC structures at room temperature.…”

Section: Introductionmentioning

confidence: 68%

Cross-Linked Liquid Crystalline Polyimides with Siloxane Units: Their Morphology and Thermal Diffusivity

et al. 2013

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Cross-linked liquid crystalline (LC) polyimides with siloxane units have been developed as high thermally conductive materials. The relationship between their thermal diffusivities and film morphologies was investigated. The crosslinking reaction of the LC polyimides was monitored by Fourier transform infrared spectroscopy and differential scanning calorimetry. It was found that the cross-linked LC polyimides successfully maintained their LC structures at room temperature as confirmed by polarized optical microscopy and wide-angle X-ray diffraction (WAXD). The thermal diffusivity of the films in the thickness direction measured by a temperature wave analysis method increased gradually from 0.116 to 0.185 mm 2 s −1 with the increasing extent of the crosslinking. In the detailed WAXD study, the obtained cross-linked LC polyimide films showed that the polymer chains vertically aligned in the thickness direction of the films, and the increase in the extent of the cross-linking expanded the areas of chain alignment. Such a chain alignment plays an important role in the phonon conduction in the thickness direction of the films.

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Section: Introductionmentioning

confidence: 68%

Cross-Linked Liquid Crystalline Polyimides with Siloxane Units: Their Morphology and Thermal Diffusivity

et al. 2013

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“…1b) detected a sharp endothermic peak (peak temperature z159 C) upon heating, most probably due to a mesophase transition of long-range order of naphthalenediimide mesogens as in the liquid crystal of polyimides. 18,19 Thirdly, the AFM phase image of 3 (Fig. 1c) displayed distinct hydrophobic (bright parts)/hydrophilic (dark parts) micro-phase separation in a bicontinuous manner which was usually observed in amphiphilic block copolymers; 20 the bright parts were assigned to the aggregates of hydrophobic naphthalenediimide cores along with the aliphatic arms while the dark parts were assigned to the aggregates of hydrophilic sulfonated units accompanied by water molecules.…”

Section: Self-assembly Of Polymermentioning

confidence: 80%

Proton-conductive polyimides consisting of naphthalenediimide and sulfonated units alternately segmented by long aliphatic spacers

Zhang

2014

J. Mater. Chem. A

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Sulfonated polyimides (SPIs) consisting of naphthalenediimide and sulfonated units alternately segmented by long aliphatic spacers have been facilely synthesized. Such an unprecedented molecular design of SPIs avoiding conventional aromatic-type imide units allows the stacking of naphthalenediimide moieties and aggregation of sulfonate groups simultaneously, imparting high conductivity and excellent hydrolytic stability.

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“…However, several studies have indicated that PIs synthesized using six-membered ring dianhydrides, like 1,4,5,8-naphthalenetetracarboxylic dianhydride (1,4,5,8-NTDA), exhibit better thermal stability due to their more stable six-membered ring structure. [24][25][26][27] Regarding mechanical strength and structural diversity, fivemembered dianhydrides with different functional groups can contribute to distinct features. 28,29 However, the impact of ring structures and conjugations on PIs' dielectric properties hasn't been unveiled.…”

Section: Introductionmentioning

confidence: 99%

“…In most cases, PI films are prepared from five‐membered dianhydrides owing to their high reactivity. However, several studies have indicated that PIs synthesized using six‐membered ring dianhydrides, like 1,4,5,8‐naphthalenetetracarboxylic dianhydride (1,4,5,8‐NTDA), exhibit better thermal stability due to their more stable six‐membered ring structure 24–27 . Regarding mechanical strength and structural diversity, five‐membered dianhydrides with different functional groups can contribute to distinct features 28,29 .…”

Section: Introductionmentioning

confidence: 99%

Impact of ring structure and conjugation on the dielectric properties of polyimides at a high frequency of 10–40 GHz

Wu,

Chang,

Liu

et al. 2024

Journal of Polymer Science

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Polyimides (PIs) are widely used materials due to their high thermal stability and potentially low dielectric constant (Dk) and dissipation factor (Df). However, Dk and Df values tend to increase at higher frequencies. Therefore, there is a significant need to reduce the Dk and Df values of PIs, which is the main purpose of this study. This research considers multiple factors, including the ring structures and conjugations on the conformation of the PI backbone. The effects of five‐membered and six‐membered PIs and the conjugated length of benzene and naphthalene structures in the repeating units on the thermomechanical and dielectric properties are systematically investigated. As a result, the PI with a six‐membered imide contributes to higher thermal stability, with a glass transition temperature higher than 350 °C, a thermal decomposition point of 529 °C, and a lower Dk of 2.7–2.8. Still, it exhibits a lower molecular weight than that of a five‐membered imide. On the other hand, PIs with esterified structures show an extremely low Df value, 0.002–0.005. This situation can be attributed to the vital correlation between the Df and the volumetric dipole moment. This study also presents the different properties arising from ring structures and conjugations. Meanwhile, the relationships between Dk and volumetric polarizability and between Df and volumetric dipole moment are confirmed. This work provides a guideline for the structure−dielectric relationship of PI at a high frequency of 10–40 GHz.

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The synthesis and thermal, optical and electrical properties of novel aromatic–aliphatic five- and six-membered thermotropic polyimides

Cited by 11 publications

References 30 publications

Cross-Linked Liquid Crystalline Polyimides with Siloxane Units: Their Morphology and Thermal Diffusivity

Cross-Linked Liquid Crystalline Polyimides with Siloxane Units: Their Morphology and Thermal Diffusivity

Proton-conductive polyimides consisting of naphthalenediimide and sulfonated units alternately segmented by long aliphatic spacers

Impact of ring structure and conjugation on the dielectric properties of polyimides at a high frequency of 10–40 GHz

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