Aromatic polyimides (PI) with low‐dielectric constant are becoming more and more important with the continuous development of high‐speed communication technology. Herein, high fluorine‐containing PI with low‐dielectric constant was prepared. First, a novel aromatic diamine monomer 4,4′‐(3,3′‐bis[trifluoromethyl]biphenyl‐4,4′‐diyl)bis(oxy)bis(3‐[trifluoromethyl]aniline) bearing multi‐trifluoromethyl groups (12FDA) was synthesized and characterized. Subsequently, a series of PI with high‐fluorine content (HFPI) were obtained by two‐step polymerization of 12FDA with three commercial dianhydrides. The polymer films cured at a maximum temperature of 310°C showed excellent thermal and mechanical properties with high‐glass transition temperatures (>250°C) and high‐storage modulus (> = 2.0 GPa). The 5% weight loss temperatures of HFPIs were all above 500°C, which indicated that HFPIs exhibited excellent thermostability. Meanwhile, HFPI exhibited low‐water absorption (<0.3%) and low‐dielectric constant (2.40–2.68 at 1 MHz). The excellent thermal, mechanical, and electrical properties make it a promising dielectric material in electronics and communication industry.

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Highly cross-linked thermosets have been extensively studied for their good thermostability and low coefficient of thermal expansion (CTE). Herein, multibenzocyclobutene (multi-BCB) functionalized silane monomers and the related thermosets as polyarylsilane are reported. These silane monomers can be cured at a high temperature above 200 °C. After curing, the corresponding transparent thermosets showed good thermal property. The results indicated that more benzocyclobutene (BCB) groups on the corresponding silane monomer induced a higher cross-linked structure, which contributes to improve heat resistance, glass transition temperature (T g), and dimensional stability. Particularly, the cured tetra­(benzocyclobutene-4-yl) silane (SiB4) showed extremely high T g over 400 °C, high initial storage modulus, and good thermostability (T d5 = 532 °C). The cured SiB4 also showed excellent thermomechanical properties with a low CTE at 24 ppm/°C. These polymers also showed good dielectric properties with a low k below 2.70. The low-k material with a low CTE may be a good candidate for high-performance composite resin matrix and high-density substrates.

Although hyperbranched polysiloxanes have been extensively studied, they have limited practical applications because of their low glass transition temperatures. In this study, we synthesized benzocyclobutene-functionalized hyperbranched polysiloxane (HB-BCB) via the Piers-Rubinsztajn reaction. The synthesized material was cured and crosslinking occurred at temperatures greater than 200 °C, forming a low-k thermoset resin with high thermostability. The structure of the resin was characterized using nuclear magnetic resonance (NMR) spectroscopy, viz. 1 H NMR and 13 C NMR spectroscopy. 29 Si NMR spectroscopy was used to calculate the degree of branching. Differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis revealed that the cured resin possesses good high-temperature mechanical properties and exhibits a high thermal decomposition temperature (T d5 = 512 °C). In addition, the cured resin has a low dielectric constant (k = 2.70 at 1 MHz) and low dissipation factor (2.13 × 10 −3 at 1 MHz). Thus, the prepared resin can function as a low-k material with excellent high-temperature performance. These findings indicate that the performance of crosslinked siloxane is significantly attributed to the introduction of BCB groups and the formation of the highly crosslinked structure.

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