Preparation and Characterization of Light-Colored Polyimide Nanocomposite Films Derived from a Fluoro-Containing Semi-Alicyclic Polyimide Matrix and Colloidal Silica with Enhanced High-Temperature Dimensionally Stability

Abstract

Light-colored and transparent polyimide (PI) films with good high-temperature dimensional stability are highly desired for advanced optoelectronic applications. However, in practice, the simultaneous achievement of good optical and thermal properties in one PI film is usually difficult due to the inter-conflicting molecular design of the polymers. In the present work, a series of PI-SiO2 nanocomposite films (ABTFCPI) were developed based on the PI matrix derived from hydrogenated pyromellitic anhydride (HPMDA) and an aromatic diamine containing benzanilide and trifluoromethyl substituents in the structure, 2,2′-bis(trifluoromethyl)-4,4′-bis [4-(4-aminobenzamide)]biphenyl (ABTFMB). The inorganic SiO2 fillers were incorporated into the nanocomposite films in the form of colloidal nanoparticles dispersed in the good solvent of N,N-dimethylacetamide (DMAc) for the PI matrix. The derived ABTFCPI nanocomposite films showed good film-forming ability, flexible and tough nature, good optical transparency, and good thermal properties with loading amounts of SiO2 up to 30 wt% in the system. The ABTFCPI-30 film with a SiO2 content of 30 wt% in the film showed an optical transmittance of 79.6% at the wavelength of 400 nm (T400) with a thickness of 25 μm, yellow index (b*) of 2.15, and 5% weight loss temperatures (T5%) of 491 °C, which are all comparable to those the pristine ABTFCPI-0 matrix without filler (T400 = 81.8%; b* = 1.77; T5% = 492 °C). Meanwhile, the ABTFCPI-30 film exhibited obviously enhanced high-temperature dimensional stability with linear coefficients of thermal expansion (CTE) of 25.4 × 10−6/K in the temperature range of 50 to 250 °C, which is much lower than that of the AMTFCPI-0 film (CTE = 32.7 × 10−6/K).

Preparation and characterization of colorless and transparent semi‐alicyclic fluoro‐containing polyimide nanocomposite films with enhanced high‐temperature dimensional stability via incorporation of colloidal silica nanofillers

“…Although the incorporation of the rigid amide units could efficiently decreased the CTE values of the afforded CPI films, the deterioration of the optical properties, including the decreasing optical transmittance in the visible light region, the increasing yellow indices, and the increasing optical retardation of the CPI films are still observed in our previous work 26–28 . This might be due to the enhanced charge transfer (CT) interactions in the molecular structures of the amide‐bridged CPIs caused by the highly conjugated and polar structures of the amide or benzanilide units 29 . In view of the limitation of the structural modification for the low‐CTE CPI films, the composition modification; that is the low‐CTE nanocomposite CPI films have attracted increasing attentions in recent years 30 …”

Polyimides with ultra-low coefficient of thermal expansion derived from diamine containing bisbenzimidazole and bisamide

“…14,15 Among them, changing the structure of polyimide is mainly achieved by designing and synthesizing aromatic polyimides with rigid rod-shaped structures, in order to obtain flatter molecular chains and tightly stack molecules, thereby reducing the free volume of the polymer and obtaining low CTE. 16–18 According to previous reports, poly (benzimidazole imide)s (PBIIs) have shown good heat resistance, dimensional stability, and mechanical properties due to their rigid skeleton and strong chain-chain interactions. 19–21 With strong intermolecular hydrogen bonding and charge transfer (CT) interactions, PBIIs can reach high T g above 400 °C, but their CTE values slightly higher than 10 ppm K −1 cannot fully meet the requirements of substrate processing technology for high dimensional stability.…”