Thymol-Derived Trifunctional Epoxy Resin with Outstanding Thermomechanical Properties and Low Dielectric Constant: From High-Throughput Synthesis to High-Performance Thermoset

The quest for high-performance and low-cost biobased epoxy resins will boost the sustainable development of epoxy resins and related applied materials for the future. Herein, starting from less expensive, readily available, renewable thymol, a biobased triphenol intermediate (TP) is synthesized in a high-throughput manner through a simple and efficient way, and then TP is converted into a targeted trifunctional epoxy monomer (TPEP) with a high epoxy value of 0.519 mol/100 g. TPEP is cured to a thermoset by using 4,4′-diaminodiphenyl sulfone (44DDS) as a hardener, and the properties are compared with a standard bisphenol A epoxy (E44). Results from curing kinetic analysis demonstrate that TPEP/44DDS can be well cured in a short time at a higher temperature (>180 °C) with excellent storage stability at room temperature and could be formulated into a single-component epoxy system to ease storage and applications. Compared with E44/44DDS, TPEP/44DDS has excellent overall properties, such as the ultrahigh Tg of 239 °C (DMA), outstanding storage modulus (739 MPa at 30 °C above Tg), decreased dielectric constant (2.5 at 1 MHz), improved high-temperature dimensional stability and thermal diffusivity, increased water contact angle (100.6°), and similar water absorption (3.1%) and thermal stability. In summary, TPEP could be readily synthesized in a large quantity from thymol via a cost-effective way, and the cured epoxy displays multiple advantages in properties. These merits will greatly facilitate scale-up synthesis and value-added applications of TPEP. Our contribution provides a bright avenue toward high-performance biobased epoxies of industrial relevance.