Optically Transparent and Thermal‐Stable Polyimide Films Derived from a Semi‐Aliphatic Diamine: Synthesis and Properties

Abstract

A novel semi‐aliphatic diamine with bulky cyclohexyl and ortho‐substituted tertiary butyl groups (4,4'‐(cyclohexylmethylene)bis(2‐(tert‐butyl)aniline), CHMBTBA) is synthesized via Mannich and rearrangement reactions of cyclohexanecarboxaldehyde and 2‐tert‐butylaniline. Afterward, several semi‐aliphatic polyimides are prepared by the high‐temperature one‐pot polymerization of CHMBTBA with various aromatic dianhydrides respectively. The resulting PIs exhibit outstanding solubility in common organic solvents (i.e., trichloromethane, etc.) and are easily processed into light color or colorless transparent films (thickness: 25 ± 1 µm) by the blade coating of polymer solution. The transmittance of all resulting films is above 86% in the visible light region (400–760 nm). Their glass transition temperatures exceed 310 °C and reach even to 374 °C (by differential scanning calorimetry). They also display low water absorption (0.29–0.87%) and good mechanical properties (tensile strength: 50.9–87.7 MPa, Young's modulus: 2.0‐2.5 GPa, elongation at break: 3.8–7.6%). Thus, they are promising potential candidates for flexible display substrates.

Soluble and transparent polyimides with high Tgs from a new semi-aliphatic diamine with cyclohexyl and ortho-methyl groups

“…The water absorption rates of PI-H(1-5) films were in the range from 0.99 to 2.45%, which were lower than that of the commercial Kapton film (3.1%). 34…”

“…Comparing to our previous work, the T g s were enhanced when the ortho tert-butyl was replaced by the ortho-methyl. 34 At the same time, the solubility of PIs was remained fairly and the cost could be reduced.…”

“…[28][29][30] Fortunately, it is considered an effective way that incorporating bulky pendant groups into PIs to improve their processability and transparency, and meanwhile maintain their high thermal stability. [31][32][33][34] In previous work, we found that the introduction of cyclohexyl and tert-butyl groups into PIs was able to increase their T g s, solubility and transparency, 34 but the cost was relatively high. In order to decrease the cost and further enhance the T g s of PIs, we intend to use methyl instead of tert-butyl.…”

Numerical Analysis of a Ito Based Circularly Polarized Optically Transparent THZ Antenna Employing Characteristic Mode Analysis

“…The characteristic mode theory (CMT) was first launched by Garbacz and Turpin in 1970s [23]. Later a distinct technique to apply the CMT to metallic [24], dielectric, and magnetic structures [25][26][27][28][29][30][31][32][33][34] was reported by Harrington et al After that, CMA based on CMT has gained a great momentum to design different antennas and explain their operation mechanism properly [26][27][28][29][30].…”

Universal Patterning for 2D Van der Waals Materials via Direct Optical Lithography

“…Polymer substrates are generally degraded or approach glass-transition temperature around or below 300 °C, which is not sufficient to entirely pattern vdW materials in a short pulse. [17][18][19][20] This is an obstacle to using the flexible nature of 2D vdW materials with flexible polymer substrates. Moreover, biocompatible materials are generally degradable in various solvents, so it limits bio application of vdW materials since fabrication of biocompatible device through conventional process is prevented.…”