Silicon-containing branched chains active esters as curing agents to improve dielectric properties of epoxy resin

C–Si bond was widely used to enhance the dielectric characteristics of polymers owing to its inherent low polarity. However, the potential of silicon-containing branched chains for modifying epoxy resins has been rarely explored. In this research, two active esters with silicon-containing branched chains of different chain lengths (DASIO, DASIOL), and another active ester with silicon-free branched chains (DAO) have been synthesized and utilized as curing agents of DCPD epoxy resins. After introducing silicon-containing branched chains, the loss factor (D_f) value of the cured epoxy system was significantly reduced. At 10 GHz, the D_f values of DASIO/EP and DASIOL/EP systems were 6.47 ‰ and 6.82 ‰ respectively, reflecting decreases of 29.8 % and 26 % from the DAO/EP system value. With the extension of the chain length of silicon-containing branched chains, the cured epoxy system's dielectric constant (D_k) value exhibited a downward trend. When compared to the DASIO/EP system, the D_k value of the DASIOL/EP system showed a reduction from 2.84 to 2.62. The silicon-containing branched chains could improve the flexibility of the cured epoxy system. The elongation at break of DASIOL/EP system was 4.2 %, which have increased by 30 %, in comparison to the DAO/EP system. In addition, through introduction of silicon-containing branched chains, the cured epoxy system also showed improved thermo-mechanical properties, hydrophobic properties and thermal stability. The research findings indicated that the silicon-containing branched chains were capable of enhancing the dielectric performances of the epoxy system. Additionally, by regulating the length of the silicon-containing branched chains, a balance of mechanical properties, thermal properties, etc. could be achieved. This provided a novel approach for developing low-D_f epoxy materials in the electronics industry.