Resveratrol-Derived Liquid Crystal Epoxy Resin with Low-Dielectric Properties and Excellent Mechanical Strength and Toughness

Abstract

The application of ordinary epoxy resins is severely limited by their poor dielectric properties and toughness, and the increasing focus on sustainability calls for raw materials to be renewable. Thus, a resveratrol-based compound (AE-Res) with three active ester structures was prepared and used to cure glycidyl ethers of bisphenol A (DGEBA) and a liquid crystal epoxy monomer (BPDGE). Test results showed that the combination (AE-Res/BPDGE) of resveratrol derivatives with liquid crystal epoxy monomers exhibited an excellent comprehensive performance. The mechanical strength and toughness of AE-Res/BPDGE were improved. Specifically, the tensile strength, elongation at break, flexural strength, and impact strength of AE-Res/BPDGE were 108.45 MPa, 12.31%, 159.92 MPa, and 39.51 kJ/m 2 , which were 48.14, 164.16, 92.51, and 143.74% higher than that of BPDGE cured by commercial methylhexahydrophthalic anhydride (MHHPA), respectively. This can be attributed to the introduction of a rigid structure and flexible ether bonds generated after curing. Meanwhile, the dielectric constant (D k ) of AE-Res/ BPDGE decreased from 3.81 to 3.00 (10 MHz) compared to MHHPA/BPDGE, mainly owing to the enhanced d-spacing (4.69 vs 4.45 Å) and the absence of highly polar hydroxyl groups. In addition, AE-Res/BPDGE also exhibited good thermal stability and hydrophobicity with a T 5% of 383.22 °C, a water contact angle of 110°, and a water absorption of 0.15% because of the presence of a rigid conjugated stilbene and biphenyl structure. Due to its ease of synthesis and environmental friendliness, AE-Res could be a satisfactory alternative to commercial epoxy curing agents.

Low dielectric polymers at high frequency with bulky adamantane groups as the linker

“…As the dielectric interlayers or substrate resins of printed circuit board (PCB), low dielectric materials are required to have outstanding thermostability, high hydrophobicity, and excellent mechanical properties besides low D k and D f . 6,7 Among conventional dielectric materials, epoxy resins, 8,9 cyanate esters, 10,11 and polyimides 12,13 display good thermostability; however, they usually possess a D k value of above 3.0 and a D f value of around 0.01. Although polytetrafluoroethylene (PTFE) has a D k value of 2.0–2.2, the processability and thermostability need to be improved.…”